This page shares test results after my associates and I tested most current small shop dust collectors and cyclone separators. We tested both airflow and fine dust separation. Ample airflow picks up the sawdust and chips. Ample filtering means that the dusty air we collect loses most of the harmful dust before it gets put back into our shops. Sadly, the results of our testing Decades of air engineering refined the minimum airflows needed at each type and size of tool to provide good dust collection. The top dust collection firms share the airflows they found we need at . Most small shop stationary tools get fairly good sawdust and chip collection with an airflow of about 350 cubic feet per minute (CFM) airflow. clearly shows most tools requireThe large commercial firms who guarantee More than twenty years of commercial dust collection Capturing the airflow Airflow testing that rates small shop dust collectors and cyclones on the two things that are . It shares the dust collector airflow tests I helped setup and Michael Standish published in Fine Wood Working magazine. It shares the same tests done on all major brands and sizes of cyclones for the sequel article that the vendors blocked from being published because that second article tested the accuracy of the vendor claims that their systems provided good fine dust collection and protected our health. During my prior and most current testing Unlike the vendor paid for magazine tests that often use apple versus orange comparisons, this testing shares accurate consistent level playing field results. Moreover, this information also includes careful testing with certified calibrated air quality meters that show how well these systems functioned in small shops. Although I started this testing in early 2001, little changed because the to fill that need. It gave the best information available and stayed current in spite of my health problems forcing me into an early medical retirement neither able to afford nor physically keep up with much testing. The vendor community made keeping the testing current easy because they just kept copying each other and selling the same “chip collection” dust collectors and cyclones that we already know create dangerously high amounts of airborne fine dust.

Introduction

This page started as a collection of comments made by users of the various small shop dust collection options and it worked poorly because the information was too emotional without any facts to support the opinions. Many of those who were the strongest supporters of a particular dust collection solution soon became even stronger speaking out against those same units within a year or two.

This emotional issue became even more heated when my university engineering instructor friends and I shared the results of our testing. Our testing through early 2005 showed all of the hobbyist dust collectors, cyclones, and filters were advertised with maximum claims far beyond their real performance when in use explaining why government testing finds almost all small shops with airborne dust levels well above the levels that forced OSHA to put in place its 1989 allowable limits for airborne dust.. Small shop vendors have known about these problems for at least ten years but with no government requirements and no push from us as their customers, they keep selling the same tools and dust collection equipment that does not protect our health. The only fine dust protection we are going to get is what we provide ourselves. We must figure out what we need then buy and assemble the pieces ourselves to build our own working fine dust collection solutions. I recommend starting with my Dust Collection Basics web page to help you decide what level of dust collection you want followed by using the Deciding Needs page to help you understand what equipment you need.

Standards

In the 1960s insurance data began showing all commercial woodworkers eventually develop fine dust related health problems, many sufficiently serious that roughly one in eight was forced into an early medical retirement. After a long fight the U.S. Department of Labor, Occupational Safety and Health Administration (OSHA) finally established a set of air quality standards in 1989. Almost nobody has been happy with the OSHA standards since. OHSA permitted dust levels are measured in terms of average weight per cubic meter of air over an eight hour period with that weight not to exceed an average of 5 milligrams and no fifteen minute period to exceed more than 15 milligrams. These standards only apply to woodworkers in the largest facilities and are five times what industrial hygienists recommended and fifty times higher than medical experts recommend. Insurance data and medical studies show almost all commercial woodworkers protected to OSHA standards still develop dust related health problems that continue to force one in fourteen into an early retirement. The argument that these problems were from earlier exposure long ago died because far too many younger woodworkers never exposed to previous higher permitted exposures become ill. With no other choice than to lose liability suits, many larger commercial firms have voluntarily adopted the five times more stringent ACGIH air quality standards. Medical testing shows these higher standards are still not ample. The European community adopted the recommended medical standards that are fifty times more stringent than current OSHA standards and ten times tougher than the ACGIH standards. All this is fine for woodworkers in OSHA regulated large commercial facilities. OSAH requirements do not apply to the six out of seven professional woodworkers and almost all hobbyist woodworkers who work in small shops. The OSAH requirements only apply to very large commercial concerns and set no oversight, controls, or requirements on the vendors that sell tools and dust collection equipment to small shops. OSHA is working on revisions to their standards but it is a long difficult fight impeded by politics. We remain unprotected except for what we choose to do for ourselves and most of us are unaware of the risks or what we need to do to provide good protection.

Health Dangers

Medical research done after the OSHA standards were established found wood dust is far more harmful than most suspected. The medical research shows every exposure to fine airborne wood dust causes some measurable respiratory damage and loss of respiratory function which accumulates over time eventually creating serious long term health problems. Although airborne dust can be up to 50-microns in size, most airborne dust is smaller than about 30-microns, roughly one third the thickness of a human hair. Our bodies do a good job of eventually getting rid of particles of roughly 10-microns and larger, but the research is clear exposure to these larger particles poses the highest cancer risk. Ten microns is about as small as we can see without magnification unless the dust is highlighted by a beam of sunlight or a laser pointer. The particles sized 5 to 10 microns tend to lodge in our nasal and throat tissues were our bodies have a difficult time getting rid of them. The particles sized up to 5-microns get past our natural defenses and lodge in our lung tissue. Particles sized 1-micron go directly from our lungs into our blood and can lodge anywhere in our bodies. There are so many medical studies showing the potential health risks from this fine particle matter they are now known as PM. Fine wood dust particles are particularly unhealthy to have on our skin and breathe because many common woods are sensitizing agents. Most start with no or mild allergic reactions to these woods, but with these particles stuck in our tissues we become more and more sensitized developing worsening reactions that can grow to seriously health threatening with time and exposure. Wood dust also contains high amounts of silica better known as glass because trees use silica for strength. These fine glass particles create long term problems very similar to asbestos and fiberglass insulation exposure. Because it often takes a decade or more before the more serious symptoms begin to appear, most ignore fine dust exposure. If you do not understand the danger of exposure to these finest particles, please look at my Medical Risks web pages for more information or do a Google Internet search on PM 2.5 health risks to see over 30 million references to the risks you can read for yourself. In short if you work with wood and do not protect yourself, the odds are 100% you will eventually develop health problems that affect the quality of your life and at typical small shop dust exposure the odds are about one in eight that these problems will be debilitating.

Risk

Sadly, small shop and hobbyist woodworkers who think our little woodworking makes for little risk often have the highest fine dust exposures. This finest dust tends not to present too much of a problem for woodworkers in large commercial facilities regulated by OSHA because commercial building codes and fire regulations require putting most commercial dust collection equipment outside where the fine dust just blows away into the outside air. Small shop woodworkers tend to have a much bigger problem because our tools fail to have hoods that control and capture the dust, our dust collection blowers move too little air for capturing the fine dust, even our fine dust collection filters freely pass the smaller more dangerous particles, and we tend to trap these fine particles indoors going months to years between thorough shop cleanings. Because this dust lingers for six months to years before it breaks down and dissipates, it builds to high levels. The airflow from our tools and dust collection systems keep launching this previous made dust that escapes collection known as fugitive dust airborne over and over. OSHA tests many small shops every year as they upgrade their licenses to larger numbers of employees and these tests give nothing but bad news. In spite of most tested small shops having the magazine rated “best” in dust collectors and cyclones with finer filters, almost all small shops particularly hobbyist shops have the highest airborne dust levels consistently testing with two to five times higher average airborne dust levels than permitted by OSHA. Worse, when medical particle counts are tested, our small shops test with an average of over 10,000 times the particulate counts recommended as medically safe. While using the top rated cyclone with even better fine filters than that maker provides, the dust level in my shop put me in the hospital. Follow up medical air quality testing showed my shop had double the OSHA allowed average airborne dust maximum with a medical airborne particle count that was 12,000 times higher than respiratory doctors say is safe.

When I had that testing done I did not anticipate writing these web pages, so did not amply document those findings. After many complained that this dated information did not apply to them, I purchased a calibrated and very expensive set of test gauges then tested the air quality in 28 hobbyist woodworking shops in California during the last quarter of 2006. This testing evaluated shops with just about every current major make and size of dust collector and cyclone, but with at least three major firms threatening me my attorney declined to allow me to publish the specific vendor names and models. Every shop tested that did not have a good hood to block, control, capture, and direct the dust from their table saw failed with airborne dust levels at least double the OSHA allowed maximums regardless of size and type of dust collector or cyclone including use of some big 5 hp cyclone units. Most shops including those with vendor designed and supplied ducting had serious ducting design errors that resulted in poor airflow to larger tools and insufficient airflow situations that led to build up of dust piles in the mains. These piles are known to pose a fire risk and when they break loose harm impellers, motor bearings and filters. The two open shops without dust collectors that relied on big fans and air cleaners both went well over double the OSHA allowed maximum airborne dust levels. This verified for me the air engineering advice that unless we collect the fine dust at the source as it is made, we are not going to be able to amply control it. Most shops had such a large buildup of fugitive dust that escaped prior collection efforts that just turning on the dust collector or cyclone without doing any woodworking pushed the airborne dust levels well over the ACGIH standards which are five times tougher than the OSHA regulations. Only one shop with a traditional dust collector tested with below OSHA airborne dust levels and that was because that shop vented outside. No shop with a 2 hp or smaller cyclone stayed below OSHA allowed maximum airborne dust levels regardless of brand and filtering presumably because of a combination of moving too little air and too open filters. Only those shops that used cyclones of my design or that vented their 3+ hp cyclones outside stayed under the OSHA air quality guidelines. Only one shop that used my recommended ducting layout and hoods with a 5 hp cyclone that was not my design but used most of the changes from my Cyclone Modifications pages (without either my permission or any credit at all) was able to keep the air quality under the ACGIH recommendations. Only the two shops that used my cyclone design with recommended fine filters stayed within medical air quality recommendations.

Problems

The reasons our shop airborne dust is so high are pretty simple. Our vendors have no oversight or certification requirements to ensure their solutions work and we do not demand through our purchases tools that amply protect our health. As a result, most small shop vendors only sell tools, dust collectors, and cyclones that are only appropriate for “chip collection” meaning getting the same stuff we would otherwise sweep up with a broom. Our tools mostly spray the fine dust all over before it can be collected. Likewise, our chip collector dust collectors and cyclones move too little air to effectively collect this dust as it is made. Most small shop dust collectors and cyclones come with open filters that pass most of the airborne dust right through. Most fine filters are too small in area so soon quickly self-destruct to also soon pass the airborne dust right through. As a result almost all small shop dust collectors and cyclones become “dust pumps”. This dust lingers for months and our foolishly trapping this dust inside our closed shops allows it to build to dangerously unhealthy levels where the airflow from our dust collection equipment and tools launches the finest invisible dust airborne every time we turn on our tools. My medical air quality inspector said the only reason our small shops do not test even higher is the air can’t hold more dust. We end up exposing ourselves and those close to us to dust levels much higher than those found to eventually make most commercial woodworkers ill, many seriously.

Recommendations

Many ask me what I recommend. My response is fine dust collection is not rocket science, but is not intuitively obvious either. It takes quite a bit of study and hard work to move a small shop from “chip collection” that collects the stuff we would otherwise sweep up with a broom to an effective fine dust collection solution. Adding to the confusion are our vendors that almost all continue to only understand, recommend and sell the same traditional “chip collection” solutions. Fortunately much of the work to appropriately size and build a viable small shop fine dust collection solution has already been done for us by the commercial air engineers and shared so we can follow their lead.

Air engineers for the makers of the large dust collection systems and filters used in shops subject to regular air quality inspections long ago did the testing and refined their recommendations through over twenty years of practical experience as to what we must do to successfully keep the fine airborne dust levels safe. They first learned once the fine dust escapes into the shop air that dust will stay airborne as long as we keep working. It takes hours of still air to finally settle. Even with a strong exhaust fan and air cleaner running, it can take six hours or longer to clean the air enough to safely take off our masks. In short, if the fine airborne dust escapes collection at the source as it is made, we will fail inspections and get exposed to unhealthy levels of fine dust.

Collecting the fine dust is not that difficult and fortunately they shared most of what we need to do on the Internet. In brief what we need to do is either work outside or deal with the fine dust. To address the fine dust we must first modify our tools so they don’t spray fine dust all over, provide ample airflow to collect the fine dust as it is made, and then get rid of that dust. They also provided ample detail to tell us how to effectively accomplish each of these goals. We can use their efforts to determine the overhead of our shops then use commercial fan tables to help pick the right size for our dust collection blower, impeller and motor. They also have worked out filter sizing and types to help with the air cleaning issues. Because we use smaller blowers only able to collect from one machine at a time, we unfortunately need to use different ducting solutions. Likewise, because few of us blow the fine airborne dust outside and use much smaller blowers, we also must use different cyclone separation and filtering system designs. The major steps follow, but you can get far more detail by looking at my Dust Collection Basics Internet pages.

Work Outside

For new woodworkers I recommend starting woodworking as a fair weather activity where we work outside wearing a good certified NIOSH mask when making fine dust. This lets us get going without a huge cost in tools or putting our health at risk. The basic tools will be useful around the home even if woodworking turns out to not be a long term hobby. I now personally do quite a bit of my work outside using a good hand held power saw, router, jig saw, drill, orbital sander, and oscillating spindle sander with a guide system instead of my large stationary power tools. I find I can do all just as well, with far less setup, and considerably more ease especially when working with large sheet goods. Festool probably makes the nicest of these type systems and other vendors offer a range of similar offerings. I personally use the Eureka Zone EZ-Smart guide system and table. This system is so versatile my daughter and I made her a nice desk in the fall of 2005 without doing any machining or sanding indoors.

Fix Tools

Start by upgrading our tools with better hoods so they do not spray fine dust all over and upgrading our tools so they can move the needed airflow. Most traditional tools come with “chip collection” hoods that capture the chips and larger sawdust but allow the fine dust to be blown all over by room air currents and airflow from our tools, motors, fans, dust collectors, and air compressors. Fortunately, air engineers share a number of good hood designs that we can often easily make from standard HVAC ducting parts. Our hoods serve a dual role. They direct the heavier sawdust and chips to a collection port, and keep the fine dust contained and protected until it also is delivered for collection. Most tools also require bigger ports and when possible need us to upgrade to better internal ducting. Air at typical dust collection pressures is more like water and will barely compress at all. As a result, the typical much smaller “chip collection” ports or internal ducting found on most woodworking tools end up acting just like a water valve and kill the airflow needed for good fine dust collection. Because smaller commercial tools are identical to larger small shop and hobbyist tools, we can use these same modifications to fix our tools. Please refer to my Ducting pages for references on fixing our tools.

Use a Good Shop Vacuum

Most of us end up with tools with very small dust collection ports or have internal ducting that cannot be easily modified. Many make a big mistake and use reducers on their dust collectors to try and pickup from these smaller ports. This is from wrongly thinking our dust collectors will behave like our shop vacuums. Vacuums operate with about ten times as much pressure so can squeeze air through smaller ports and ducting. That is just not true for our dust collection blowers. Air at typical dust collection pressures behaves more like water and will barely compress at all. This means any obstruction, small port, undersized duct, small flex hose, or even sharp bend in our ducting will severely reduce our airflow just like a partially open water valve. Our choices are simple, either use these tools outside while wearing our masks, or get a powerful shop vacuum with an upgraded filter and use it on the smaller ports. A good rule of thumb is any port smaller than about 3.5” in diameter needs a shop vacuum connection, not a dust collector connection. Personally I found only the Festool, Fein Turbo III and Fein 18 gallon stainless of all the shop vacuums I tested move ample air with ample pressure to support good dust collection at my smaller tool ports. I chose for my use the big Fein 18 gallon stainless upgraded with a Sears red-line HEPA filter in addition to its normal fine polyester filter bag. Had I not bought one of these I would have instead bought a good commercial janitorial vacuum that generates at least 90 inches of pressure. In addition to helping with the collection, our vacuums with fine filters are important as they are about the only way that many shops can get cleaned of the buildup of residual dust missed during collection.

Provide Enough Airflow

Air engineers next found that we need to move more than double the total airflow at our larger tools with the upgraded hoods to collect the fine dust as we did to provide good “chip collection”. At first this does not make sense. Most of us know from watching dust particles in a beam of sunlight that it takes very little airflow to airborne dust. Careful testing shows it takes about 50 FPM airspeed to overcome normal room air currents and pull in this fine dust for collection. Just blowing a breath out generates more than 50 feet per minute (FPM) airspeed which is why it is so easy to move fine airborne particles. With blown air the particles keep moving until the air spreads out and is slowed by friction. Unfortunately, sucked air behaves differently. Sucking pulls air from all directions at once. As a result airspeed falls off at about the same rate as the size of a sphere expands, roughly 4 times Pi times the distance squared. We know from using our vacuum cleaners what this means. The only dust we pickup is right next to the vacuum nozzle. The same is true for our dust collection. The only way to get enough airspeed to cover enough area around out tools to capture the fine dust before it gets blown away is to move lots of air. Airspeed in FPM is related to air volume measured in cubic feet per minute (CFM) a by the simple formula FPM=CFM/Area where area is measured in square feet. Knowing how big of an area needs covered and our 50 FPM airspeed lets us calculate that we need about 792 CFM air volume as a minimum to get good fine dust collection around our larger machines. Most air engineers choose to round this to 800 CFM. Over twenty years of practical air engineering experience shows this number that 800 CFM is a good airflow to meet OSHA standards. We need closer to 900 CFM to meet ACGIH standards and about 1000 CFM at our larger tools to meet medical recommendations which are now the standard in the European Union. Likewise, this same experience shows that our ducting systems need to be sized to carry ample air with an internal duct speed of about 4000 FPM to keep the ducts clear. The roughly 350 CFM air volumes moved by 4” ducting when driven by most 1.5 hp or smaller dust collectors and most 2.5 hp and smaller cyclones is plenty ample air for good “chip collection” but no where near enough airflow to support good fine dust collection.

Air engineers tested almost every major type and size of tool to verify the airflow needs of each for good fine dust collection. Although a few newer tools that totally contain the dust during woodworking need far less airflow, most of our tools are older designs that come with no dust collection or only “chip collection” built in. These tools require more airflow. Careful testing and over twenty years of experience developed engineering tables that show how much airflow is needed at each type and size of tool. They shared what they learned as Tool CFM requirement tables. Because our larger small shop and hobbyist tools are identical to smaller commercial tools we can use these same CFM requirement tables. Additional testing shows we need about 12.5% more airflow to meet the five times tougher than OSHA air quality standards and about 25% more than OSHA airflows to meet the fifty times higher medical air quality standards. The cost to upgrade is so low that most small shop owners should go ahead and spend the little extra on their systems to support the medical air quality standards.

Blow the Dust Outside

Air engineers recommend separating off the sawdust and chips followed by getting rid of the fine dust by blowing it away outside where it quickly disperses. Air engineers realized long ago that trying to filter the air is not quite so easy and creates a nightmare of problems. This means almost all small shop owners should blow the fine dust away into the outside air just like large commercial facilities. Commercial building codes and fire regulations require putting dust collectors and cyclones units outside. Most airborne dust is made up of particles 30-microns or smaller. A 30-micron particle is about one third the thickness of a human hair. Almost all commercial dust collector filters are rated at 30-microns, meaning they freely pass airborne particles right through. With these units having to be outside the airborne dust just blows away right through the filters into the outdoor air. Even when we blow the fine dust outside, we still need to regularly blow our shops out thoroughly to keep the inevitable dust that escapes capture from building up to dangerous levels.

Chip Overflow

Putting sawdust and chips directly on our plants and gardens can kill our plants, so we should separate off this stuff, then either compost or discard depending upon wood type. Most find a cyclone as the best way to separate off the heavier sawdust and chips. Most commercial cyclone makers use cyclones either with automatic bin emptying systems or open filter bags on the cyclones because a full bin will cause a cyclone to pass all the sawdust and chips right through. Most small shop woodworkers should use a large open felt bag if they have problems overfilling their cyclone dust bin.

Heating and Cooling

Too many foolishly worry about blowing the heated air out of their shops when commercial firms have shown that doing so really is not as expensive as trying to filter the air. Large commercial shops with huge blowers that turn over the entire air volume many times every hour have shown for years that a good radiant heater will leave us feeling little discomfort unless it is below freezing outside. Air engineers found that with radiant heaters blowing the air outside does not create a heating problem. It does create problems if a shop needs air conditioned. Small shop professionals and hobbyists can and should also blow our dusty small shop air outside, but with a caution. Blowing outside will exhaust so much air it can suck deadly carbon monoxide backward through our stoves, furnaces, and other fired appliances, so we need makeup air and a carbon monoxide detector in our shops and homes.

Carbon Monoxide Poisoning

We do need makeup air to avoid risk of carbon monoxide poisoning. Our blowers move enough air with ample pressure that without make up air they can suck the exhaust gasses backward through our flues and vents. Most need to just open a door or window and they are fine. Everyone that blows the air outside should install a carbon monoxide detector in their shop and in their home to ensure our powerful blowers do not pull deadly carbon monoxide backward through our vents.

ExhaustApproaches

There are also two commonly used approaches to exhausting the air outside.

Blow the Dust Outside Using a Dust Collector

For those on a tight budget that cannot afford a cyclone, you can get by with a dust collector that you put outside and do not return the air inside. Because few dust collectors are made to be put outside and even when put in outside rooms, create a mess to maintain, I don’t recommend this solution. Dust collectors give us frequent dust baths when emptying the bag and cleaning the filter, plus we have a hard time knowing when an outside filters are getting full. Commercial air engineers consistently tell their customers to use cyclones instead of dust collectors. They learned that putting dust collectors outside gets rid of the fine dust but creates a constant problem with emptying and cleaning the filters, plus filter cleaning creates far too much fine dust that ends up often back in the shop.

Blow the Dust Outside Using a Cyclone

Almost all commercial shops subject to air quality inspections choose to use a cyclone to blow the fine dust away outdoors with no filter. Using a cyclone also continues to be the least expensive and best solution for small shops. Commercial cyclones are very carefully engineered to drop the chips and heavier sawdust into a dust bin and then use high internal turbulence and a separation design that separates off near 100% of the fine dust to blow that dust away into the outside air.

Filter the Air

Many of us have concerns that keep us from putting our dust collector outside or blowing the dirty air outside, so we instead need to filter our air. Filtering the air is rarely done by large commercial shops because filtering opens a bucket of worms. Most large commercial firms either use outdoor cyclones with no filters, or large bag houses that use very open cloth filters. Both just let the fine airborne pass right through and blow away outdoors. Filtering requires buying expensive large filters that require constant maintenance and frequent replacement if we want to minimize our exposure to the finest unhealthy dust. To ensure our filters provide ample fine dust filtering, they must stay clean enough that they do not kill the airflow needed for good fine dust collection. We also must regularly monitor and replace our filters when they begin passing fine dust because cleaning rapidly wears filters out opening their pores allowing them to pass more unhealthy dust. Also we should regularly blow out our shops thoroughly, especially after making lots of fine dust, to ensure the finest near invisible dust does not build to dangerous levels.

Air engineers do share expert information on how to configure our filters. When designing systems for indoor use where the air is filtered and returned inside, air engineers defer to the standards set by medical experts. The medical hygienist society ACGIH recommends cleaning the air to a standard that is five times cleaner than allowed by OSHA. The medical doctors and respiratory medical researchers recommend cleaning the air fifty times better than required by OSHA. The medical folks recommend filtering to 0.5-microns with brand new clean filters tested and certified by an independent testing laboratory. They also recommend wearing a NIOSH approved removable cartridge filtered face mask whenever making fine dust. My respiratory doctor agrees with wearing a mask, but says those of us with existing conditions should use 0.2-micron certified filters. If you have not already done so, it is well worth your time to read over the Dust Collection Basics information that discusses filter basics to help you better choose and size your filters.

Ducting

We need to use at least 6” or larger ducting to move our needed 800 CFM and maintain roughly 4000 FPM airspeed in our vertical ducts and at least 2700 FPM in our horizontal ducts to avoid duct plugging and dangerous dust piles. This means we also need the same sized ducting to smaller tools as well because the option of opening other ports to keep the mains clean ends up killing the airflow we need for good dust collection at the tool we are using. Please see my Deciding Needs” and Ducting pages for more detail on ducting sizes and system designs. The reason we must move so much air is our dust collector and cyclone blowers move air with about one tenth the pressures of our vacuums leaving air more like water, almost totally incompressible. Just like a water valve, any restriction, obstruction, small pipe, or small port kills our needed airflow. Although this reduced airflow in a down drop may be ample to meet the CFM collection needs for a smaller tool, when that reduced airflow hits our mains, there is too little airflow to keep from building up clogs and dust piles. Ducting systems with smaller pipes create piles that can create highly explosive dust clouds when they break loose. Frequent piles will slam into and over time will ruin our blower impellers, blower motors, ducting and filters. The 4” ducting sold by most hobbyist vendors for “chip collection” is so restrictive we just cannot move enough air through it without getting a huge blower.

Dust Collection Operation

Making an informed decision on our dust collection equipment means we should know how a dust collector, cyclone, and filter system works.

Dust Collector Operation

A dust collector uses a large pressure blower to suck air then blows what it picks up into what is known as a bag tree. The blower is made up of a simple induction motor that typically turns at 3450 RPM. The motor shaft is bolted directly to a fan called an impeller. The impellers on our dust collectors are made of heavy metal capable of handling hard hits from small blocks of wood. They are also made to be fairly self cleaning explaining their name “material handling” impellers. The impeller turns in a blower housing that is spiral shaped and needs to be very smooth to minimize the disruption of airflow. The blower opening is often carefully sized to ensure our dust collectors do not try to push so much air they end up burning up the motor. Because these blowers generate so little pressure, they will barely compress air at all. This means the blower opening should be the same size as the ducting mains or airflow will get severely cut just like partially opening a water valve. The air filled with dust and chips goes into the bag tree and spins below what is known as a separation ring. In theory this ring makes the heavier blocks and chips fall permitting only the lightest dust to go up into the upper filter. In practice the airflow inside a dust collector is so violently turbulent that chips and even small blocks constantly crash into and frequently poke holes into our filters.

Cyclone Operation

In spite of what some would like us to believe, dust collection cyclones are simple tanks with no moving parts and have been used for dust separation for over seventy years. Cyclones are a special class of what researchers call swirl tubes. Cyclones are well researched and broken into seven basic cyclone types plus some hybrids optimized to separate different materials or gasses. If you want to find out more, do a Google search on cyclone design and swirl tubes.

As shown in this animated graphic, cyclones are made up of just a few parts, an air inlet, an outer cylinder, an air outlet, and cone with dust chute that connects to a collection bin. Dirty air comes in through the inlet. Almost all large commercial woodworking facility cyclones are agricultural cyclone designs that cause this incoming air to crash hard into the air already spinning inside the cyclone. The resulting very high turbulence breaks the heavier and lighter materials apart. The spinning air throws the heavier materials outward to the cyclone walls. Airflow on the cyclone walls is slowed by friction. Heavier particles get trapped in the slower moving air and gravity slowly pulls these heavier particles down. The cone on the bottom of the cyclone is angled just right to keep the airspeed constant to keep the heavier particles pressed tightly to the cyclone walls. These heavier particles continue to slide downward and eventually exit out a dust chute into the collection bin. The dust chute is sealed tightly to the bottom of the cyclone with no air leaks to stir up the collected dust. A full dust bin or bad air leak causes the cyclone to pump all right through with little or no separation. Near the bottom of the cone is a certain place called a reversal point where the spinning air without these heavier particles reverses direction with the cleaned air spiraling up through the center of the cyclone then exits through the cyclone outlet.

Dust Collection Evaluation

Assuming that we agree we need a big enough blower to move a real 800 CFM at our larger machines while overcoming the resistance of our system and then we must either send the dust outside or amply filter it, we can evaluate the various alternative solutions. To make an informed evaluation we need to first look at total airflow to ensure the blower is sized large enough to meet our shop need. We then must make a decision on either blowing the air outside or filtering. This decision should be to blow the air outside, but some like me have no choice but to filter. If the filter is not fine enough to protect our health we are wasting our time and creating an eventual health problem for ourselves and all close to us. We need ample filter area because when a filter is too small to meet our airflow, then even a good fine filter will soon get ruined from over cleaning and from fine dust getting forced through leaving our shop air filled with unhealthy dust.

Small Shop Dust Collection Product Overview

Sadly, our small shop vendors have long made their livelihoods by copying and downsizing larger commercial tools, having these tools built overseas by minimal cost labor, and then selling to small shop woodworkers. It has been my experience that most of these vendors do a terrible initial job in their copying and need years to slowly iterate through many changes to end up with a viable product. The better of these vendors follow the Japanese lead with automobiles and continue to refine their products until they actually end up with a superior and more reliable end product. The less reputable vendors only keep making changes until they have products that work for the lowest possible price.

These approaches make for a wide variation in blower performance level which is a surprise to many. Almost every U.S. made name brand blower with the same motor speed and same type and sized impeller will deliver near identical performance. The higher priced imports that have been in use for a while tend to work pretty well and deliver almost exactly the same performance as the leading U.S. made blowers. Those that are newer or of lower cost tend to deliver lesser performance with the least cost often delivering half the expected performance. The differences include poorly shaped and formed blower housings, constrictive inlets and outlets, poor quality motors that really don’t deliver advertised horsepower and speed, and roughly made parts and impellers that significantly interfere with airflow. Our testing found almost all lower cost imported blowers whether on dust collectors or cyclones, had major innumerable design, copying, and manufacturing problems built right into each unit. In short, looking at a standard U.S. blower performance table will only tell us the maximum possible performance, not necessarily what will be delivered.

Sadly, this is even truer with cyclone designs. Without pulling any punches we only found two basic cyclone designs being sold by all of the major small shop vendors. All were either copies of the larger older Delta outdoor commercial cyclone or copies of the same 1962 New York Dept of Labor, Division of Hygiene Engineering cyclone that appears to have modified this same Delta unit for indoor use with smaller motors. The original cyclones were engineered for outdoor use with monster blowers that had plenty of power to generate huge internal cyclone turbulence that broke the fine dust from the heavy and then did an excellent job of targeted separation. These designs were engineered to separate off almost all the heavier dust and chips and blow close to 100% of the fine dust away into the outside air. Downscaling this design and bringing it indoors turns these units into excellent “chip collectors”, but terrible fine dust collectors. They need roughly 3 to 5 hp motors to move ample air to ensuring capturing the fine dust at our larger tools and dustier operations. Additionally, pushing such a high load of fine dust into a fine filter that tries to trap that dust instead of letting it escape outside creates serious filter problems. Our filters plug killing needed fine dust collection airflow, need constantly cleaning that quickly wears out the filters, plus the cakes increase pressure that forces the finest unhealthiest dust right through tearing open the filter pores as it passes. Soon even top quality certified fine filters freely pass most of the finest unhealthiest dust giving rise to a false sense of security and people getting ill. This is exactly what happened to me and left me in the hospital.

Dust Collector Testing

Our dust collector testing tested to see if each dust collector moved ample air for good fine dust collection and if it provided ample filtering. As expected from our blower evaluations, of all the major advertised dust collector vendors only the Delta and Jet families of companies provided dust collectors that actually moved the airflows they advertised and only these two vendors made dust collectors with 1.5 hp motors able to move a real 800 CFM when challenged by the minimal resistance involved in moving a portable dust collector between machines. All other vendors had so many blower and dust collector design errors and poorly made parts that they needed at least 2 hp motors to move this needed 800 CFM. Sadly, one vendor did not move this much air even with their 3 hp dust collector.

We found no dust collector that came with filters suitable for indoor use. Medical experts recommend 0.5-micron filters tested and certified when clean with those of us who have existing allergies using 0.2-micron filters. Most dust collectors come with 30-micron bags that freely pass almost all the airborne dust. Those with finer bag filters and cartridge filters typically advertise 1.0 and 2.0-micron filters. Many of these claims for fine filtering come from the same few vendors whose track record is poor because their advertised claims do not match actual filtering levels. Filters pass a range of dust particles that cycles from a maximum when new and clean to a minimum when the filter is fully loaded with an internal cake of dust in the filter fibers that increases filtering. For dust collection this creates a swing of roughly twenty fold between the highest and lowest filtering provided. Most small shop dust collector “fine” filtering bags and cartridges were advertised with their maximum filtering between 0.5 and 2-microns meaning their maximum varies between 10 and 40-microns. This leaves these filters passing almost all airborne dust when new and still passing almost all of the finest unhealthiest 2.5-micron dust the rest of the time, clearly not filtering suitable for breathing. Hopefully the dust collector makers will come out with better filters that will take these units down to a more healthy range.

We also found no dust collectors with ample fine filter surface area. When fine filters are made too small they quickly plug creating constant cleaning problems. Cleaning destroys the filter pores soon opening them to also make even the fine filtered dust collectors into “dust pumps”. The only way to use these units for fine dust collection is to put them outside with no air being returned to the shop. A 0.5-micron fine bag or cartridge filter at 800 CFM airflow and the relatively “dirty” air from a dust collector needs at least 200 square feet of area but typically come with less than 30 square feet, many with just a top bag only have 15 square feet. Using a smaller filter works for a short while but soon causes undersized filters to fail from too much dust loading and excessive cleaning. Those offering cartridge filters typically offer the poly-cellulose blended filters that require roughly double the surface area as the all poly felt, so also provide less than a quarter the needed filter area.

The Jet dust collectors with their larger canister filters started a dust collector revolution that continues to have problems. The cartridges offer far more surface area than the standard bag filters so can provide finer filtering with much better airflow and lowered resistance. Thinking these units would perform similar to the cartridge conversions I at first recommended these types of units. I now recommend against them because almost all feedback on the canister collectors says they just have too many filter problems.

Although many vendors offering cartridge filtered dust collectors promise less frequent cleaning and provide their units with various flappers, beaters, and even shakers to help keep the filters clean, most find that to be advertising nonsense. The finer cartridge filters need far more surface area than provided to avoid constant plugging, so most of these units become a constant cleaning nightmare needing cleaned every few minutes of operation. Many sharp pointed chips stick in the filter pleats leaving holes in the filters. The constant cleaning and chip holes make for rapid filter wear. And the buildup of fine dust creates pressure problems that force the fine dust to tear through the filter pores opening them rapidly. Most of these cartridges start off passing fine dust, and even those that do not soon freely pass the fine dust also. In short, bag or cartridge, these dust collectors should be put outside with no air returning to our shops. If they are going outside then a good heavy felt filter with a fine weave will pass the most air and minimize cleaning overhead. For those who must use these units indoors I recommend making your own conversion starting with a good dust collector that will move at least a real 1100 CFM then adding a good 300 square foot or larger ASHRAE certified fine 0.5-micron filter and using a separation screen to protect the filters from hits from sharp chips. These filters need to be closely monitored and changed as they wear or begin to let the fine dust right through. Please see my DC conversion page for more information.

The Fine Woodworking April 2006 magazine issue #183 contains an article by Michael Standaish titled “Portable Dust Collectors”. This article refreshed the dust collector testing I am no longer able to do. This article came up with exactly the same conclusions and recommendations that we reached from our testing done in 1999 through 2002. The below graph copied from this article is easy to read and tells us which machines move ample airflow. Anything above the 400 CFM line and below the 800 CFM line is a good “chip collector”, so this graph confirms every dust collector tested provides good “chip collection”. Because the testing for this article was well done using a consistent filter that was already “seasoned” we do not have to worry about the overhead of the dust collector or its filter, but only the resistance of collecting from a large machine with a couple of ports. A good static calculator shows that this overhead resistance is about 2.3”. Looking above the 800 CFM line and to the right of about 2.3” of pressure tells us which dust collectors move ample air at ample pressure. Only the larger Jet, Grizzly, and Delta portable dust collectors that this article rates as “excellent” move enough air with enough pressure for good fine dust collection. Unfortunately, in addition to moving ample air, fine dust collection also requires either blowing the fine dust away outside or ample filtering. None of these portable dust collectors had the 0.5-micron filters recommended by medical experts and all that offered fine filters provided under 30 square feet of filter area instead of the at least 400 square feet recommended by filter makers. Fortunately, all three of these dust collectors has enough pressure to power minimal ducting in a one-car sized shop and place these units outside with no air returned to our shops. That is the only way any of these units are appropriate or safe to use for dust collection.

Cyclone Testing

Our cyclone research found all magazine ads for small shops cyclones pictured either exact or very close copies of each other. Discussion on the woodworking forums by the makers of these cyclones and people that measured the different units advertised in the small shop and hobbyist woodworking magazines confirmed that all small shop cyclones were either exact or modified copies of the 5+ hp outdoor “chip collecting” cyclones sold by Delta. These cyclones including the Delta appear to be cyclones built on plans from the New York Dept. of Labor, Division of Hygiene Engineering published in August 1962. This cyclone design has its roots in a basic agricultural cotton cyclone built with very high internal turbulence to break sand and dirt from cotton fiber. When used with woodworking these agricultural cyclones do an excellent job of “chip separation” breaking the fine dust from heavier. On average woodworking dust is made up of about 85% heavier chips and sawdust plus about 15% airborne. Airborne dust particles are typically about 30-microns and smaller which do not readily settle in normal room air currents. This cyclone design separates off close to 100% of the heavier sawdust and chips into a collection bin while and blowing almost 100% of the airborne dust particles out the cyclone top outlet. Instead of just blowing this fine dust into the outside air as is done by large commercial woodworking cyclones that automatically empty their dust bins Delta built their cyclones without the automatic dust bins and instead installed very open filters that freely pass the airborne dust. These big filters catch the chips and sawdust if the dust bin gets full because cyclones with a full bin blow everything right through. These cyclones were engineered to provide the roughly 350 CFM required a each larger tool for good chip collection. When put outside a shop with a 5 hp motor this unit does an excellent job providing good chip collection for up to three machines operating at once. To collect from more machines at once, Delta offered a variety of larger blowers and motors that worked with this same sized cyclone. I have seen advertisements for up to 12.5 hp motors, but people have written me saying they had up 15 hp motors on their Delta units.

Because they exhausted outside, quite a few were able to easily change these existing outdoor cyclones to provide good fine dust collection. The commercial dust collection firms whose customers must pass government air quality inspections have long shared their decades of experience which shows good fine dust collection requires upgrading most tool hoods to amply trap, contain, and direct the fine dust for collection, plus moving 800 to 1000 CFM at our larger tools to pull in the fine dust over a larger area. Most existing shop ducting systems only used 4” ducting to the larger tools as this is all that is needed to support the roughly 350 CFM airflow needed for good chip collection. At the low pressures that dust collection blowers provide, air is more like water and will barely compress at all so any small port, small duct, or tight bends in the ducting designs will severely limit airflow. To support the larger 800 to 1000 CFM airflows required for good fine dust collection shop owners had to upgrade to use all 6” or larger ducting. Add the very high resistance of as much as 1.5 hp motor power to force the air inside a cyclone to turn in a tight separation spiral leaves the 5 hp motor just about the smallest that can provide enough pressure to move the needed airflow at a single larger tool when working against the overhead in the longest ducting run in a full three-car garage sized shop. It takes just over a 3 hp motor to power a cyclone and the ducting typical for a two-car garage sized shop. This meant those who had the smaller 5 hp motors were able to make their cyclones work as good fine dust collectors in their small shops without a motor change. They had to upgrade their tool hoods, upgrade their ducting to all 6” or larger, and then add blast gates so that they only collected from a single machine at a time. To get good fine dust collection from multiple machines running at once or for larger shops requires considerably larger blowers and blower motors.

Small shop vendors saw this success and wrongly assumed they could simply copy these Delta cyclones as they have done with so many other tools, make their own arbitrary changes, and then end up with great dust collectors. Sadly, many of the firms that sell this type of equipment fail to do their own engineering and there are no standards or controls on their products except what customers exercise through their purchasing decisions. Most copied the typical outdoor cyclones that were engineered long before the 1989 OSHA airborne fine dust limits and testing program were established. These copies proved to be excellent chip collectors that do not move enough air with enough pressure for good fine dust collection. Word of mouth and magazine reviews are just about all we have to go on to make informed dust collection decisions and most of that information was bad. Unlike most woodworking operations that are pretty obvious, just like the vendors most woodworking authorities and magazine editors failed to take the time to learn the risks or understand the technology and science behind good dust collection. This lack of knowledge on the part of woodworkers and our experts combined with a lack of standards, no oversight, and shoddy engineering by our copycat vendors to create a nightmare mess in terms of small shop dust collection.

The traditional outdoor dust collectors and cyclone designs were downscaled poorly and sold for indoor use in ignorance of fire and explosion risks with the same wide open filter bags designed to pass close to 100% of the airborne dust. With fine wood dust taking six months to years to dissipate and break down, those small shop owners who bought this equipment build up huge dust levels that the airflows from our dust collection and tools continues to launch creating dangerously unhealthy dust levels. Many small shop woodworkers use fairly toxic woods that create worsening allergic reactions. Dust from these unhealthy woods combined with indoor use of these down scaled outdoor cyclone designs that were “dust pumps” to hurt many people, some seriously.

It is no secret that the reason I came up with my cyclone design and these Cyclone and Dust Collection Research web pages is because I was badly hurt by trusting the cyclone vendor that the magazines continue to rate as the “best” cyclone provider. Sadly, this cyclone vendor used a fear of fine dust advertising campaign to sell expensive cyclone and ducting systems. That advertising campaign proved so successful that other vendors either hired them to design cyclones or just plain copied the same cyclone design. That left the small shop market full of “chip collector” cyclones that did a very poor job of fine dust collection. Because this vendor added a fine filter, the result created a false sense of security that left shops looking cleaner while building up dangerously unhealthy amounts of fine dust that our dust collection systems and tools kept launching airborne. In addition to poor airflow and bad filtering, their cyclone and ducting design had other serious problems. By the time I finished my installation I was pretty angry because I found their unique ducting was identical to the same stuff I could buy locally for half the price, plus that duct leaked badly so took lots of my time and energy to properly seal. That cyclone plugged constantly in the cone when preparing rough stock using my planer and joiner. The ducting design was so poorly engineered the large vertical ducting runs plugged constantly and the horizontal ducting runs built up huge dust piles because the cyclone lacked the airflow to keep the ducting clear. Those piles posed a fire danger and when they broke loose slammed into and damaged my blower impeller, motor bearings, and filter.

This design was never designed to provide the separation needed to work with fine filters. Its gravely undersized fine internal filter plugged every twenty minutes when using my drum sander. As discussed before adding fine filters with too much dust destroys the filters. The smaller the filter the sooner this happens. Cleaning that filter and clearing these plugs was a messy job that left me and my shop covered in the very dust I bought that system to avoid. I did as their engineer recommended and replaced that undersized internal filter with their recommended big third party fine filter bag. Even after upgrading my unit with a “neutral vane” plus the other changes on my cyclone modification web pages still left this cyclone needing at least a 200 square foot fine polyester filter and not less than a 400 square foot poly-cellulose blended cartridge filter. Commercial dust collector manufacturers actually recommend double this surface area as that will make the filters last four times as long, reduce cleaning frequency by a factor of four and cut filter resistance four fold.

Chopping up the original design to fit these units under an 8’ tall ceiling and break down into standard shipping boxes created a nightmare of additional problems that even all my suggested changes cannot cure. The smaller the cyclone the bigger the required motor, yet small shop vendors shrank the cyclone sizes and used smaller motors. Commercial cyclones sized the same as what small shop vendors sell typically come with either a 7.5, 10 or 12.5 hp motor, but these vendors sell these units with 1.5, 2 and 3 hp motors. Putting a huge blower fan on these and testing with a wide open inlet makes them look great for testing if you don’t realize that the last two magazine tests burned up all kinds of motors from over stressing the motors by trying to move too much air. Our testing found only one 3 hp cyclone that actually moved enough air for good fine dust collection against the overhead found in a typical 2-car garage sized shop. It had all the changes I recommended, but still had serious filter problems and the normal problems caused by chopping up the original design. The only way to get a smaller motor to work with this design is to increase the cyclone diameter which kills separation efficiency putting even more dust into the filters. This also creates a cyclone too tall to fit under a normal ceiling unless you just hack up the cone and make it short. Many did just that leaving oddball sized cones that both plug when planning or doing other woodworking operations that make lots of larger chips and shavings and suck the fine dust right out of the dust bins into the filters. My OSHA inspector said most small shops with indoor cyclones end up testing with two to five times higher than the maximum OSHA allowed airborne dust levels and averaged over 10,000 times the airborne particle counts considered medically safe. These cyclones pushed indoor dust levels in hobbyist shops that do little woodworking far beyond the levels that made all commercial woodworkers ill and put one in eight into an early medical retirement. Frankly a lot of woodworkers got pretty angry and few hurt by this dismal technology including me.

Regardless of my following my cyclone vendor’s instructions and making their suggested upgrades, three months after installing that cyclone and vendor provided ducting with the improved fine external filter my woodworking landed me in the hospital. I nearly died and was left with a permanent loss of over half my lung function. Medical air quality testing showed my cyclone moved less than half the air required for good fine dust collection, my gravely undersized filter had self-destructed turning into an open sieve that freely passed most of the airborne dust, my ducting was so poorly designed it lacked the airflow to keep the ducting clear, my cyclone provided no better separation than the trashcan separator lid it replaced, and my vendor totally “forgot” to advise me of the need to upgrade my tool hoods so even had the cyclone worked with ample airflow there was zero chance of my shop having the good fine dust collection they advertised.

Good Options

Although many choose to use smaller dust collectors, small cyclones, and other options, the bottom line is you need to move enough air to capture the fine dust at the source, use good hoods, and then either blow the air away outside or provide ample filtering. Most small shop dust collectors and cyclones are challenged both in airflow and filtering to be suitable for fine dust collection. Many new cyclones compromise both on airflow and filter size. Although smaller filters work, the tradeoff becomes how often we have to replace these expensive filters.

Today I believe small shop owners have more and better fine dust collection options, but most hobbyist vendor supplied dust collection systems still have various concerns ranging from insufficient airflow, poor separation, filter plugging, poor filtering, cyclone cone plugging, sucking the dust out of the dust bins, building up dust piles in the ducting, on and on. My experience in getting usable feedback from owners of these units left me feeling like a hyper ping pong ball. After spending a thousand or more on cyclone and ducting, woodworkers claim their purchase as the best or worst ever. In testing these units with an air gauge, barrel of certified fine dust and a scale, the results were very unimpressive. The typical hobbyist dust collector and cyclone moved about half the advertised airflow with minor to serious filtering problems. Most cyclones provide insufficient separation for use with fine filters. These dust collectors and cyclones in my opinion are only suitable for outside use with wide open bag type filters just like the units that most copy. Many found in their own use these same concerns and raised these issues with their vendors. Most said their concerns were passed off by their vendors as poor testing, bad setup, or not understanding the physics and proper testing protocols. Frankly, as a group the whole bunch of hobbyist vendor supplied dust collectors and cyclones would gravely fail to measure up if the US adopted the much more stern new European air quality standards. I doubt if more than the top few would actually keep the fine dust levels amply down enough to even pass US OSHA testing. With most dust collectors and cyclones actually increasing the airborne dust levels, I continue to only recommend the following three units for indoor use with filters. Here are summaries of comments made by the owners of these few units.

Felder RL Dust Collectors

All of the cyclone problems reopen the idea of just buying a top quality dust collector. There are not many choices. Of all the dust collectors I reviewed prior to 2005 only the Felder RL-160 Series Clean Air dust collector actually moved ample air and provided the filtering to make it a good indoor fine dust collection system. I presume their newer even larger RL-200 would perform even better. Since my original review Felder changed its RL-125 dust collector pictured to the left to also move ample air for good fine dust collection. Unfortunately, the feedback I’ve received from those who have tried this smaller unit, say it really is too small both in airflow and chip capacity. Those with the money rave positively about their new clean air Felder RL series collectors that provide a staged fine dust filtering setup to be suitable for indoor use. Some of the Felder RL dust collectors come with a muffler as standard equipment. Although the maker claims these units have the capacity to run more than one machine at a time, the RL-125 specifications show it clearly does not and the RL-160 looks marginal to run two larger tools concurrently. The price tag on these units was very acceptable for when I owned a shop and cheap for those with respiratory problems. I asked John Renzetti who uses one of these Felder units to share a little review. Here is what he shared.

Felder introduced the RL series dust collection system in 2002. The development came about as a result of much stricter standards for emissions in Woodworking shops in Germany. The German health authorities found a high rate of nasal cancer especially in those shops that returned the air directly to the shop. Felder submitted the machine to the German Government Health department for certification as a clean air dust extractor, and received approval from the BG test authority. The ratings put out by Felder are from these tests, which tested emissions and CFM of the machine with dirty filters, and flex hose with 90 degree bends.

Dust and chip laden air is drawn into the intake port. Vacuum pressure pulls the heavier chips down into the bin, while the dust-laden air is pulled up through a bank of HEPA type filters. The clean air is then pulled through the fan blower and exhausted. The cost of the RL dust collectors will probably put them beyond the budget of most hobbyist shops. The RL125 is around $2000, while the RL160 is close to $2500.

Woodsucker II Cyclone

WoodSucker which appears to no longer be in business and its founder Larry Adcock deserves high praise for helping to change the dismal shop dust collection market. It is no secret that six out of seven professional woodworkers and most hobbyist woodworkers work in shops that are mostly not subject to either fire marshal inspections or air quality testing. Most of the mass marketed import firms sold smaller indoor copies of commercial dust collectors and cyclones that had to be kept outside to pass fire marshal inspections. Bringing these units inside was building up huge amounts of fine airborne dust with the typical shop according to OSHA testing running two to five times more than the maximum allowable airborne dust levels. OSHA air quality testing was only required of the largest commercial woodworking facilities, so most of this market continued to use dust collectors and cyclones that only did “chip collection” meaning collecting the sawdust and chips amply to pass fire marshal inspections. With the small few person woodworking shop market collapsing due to pressure from large manufactures and off-shore competition, one of the cyclone suppliers to these small firms that only did “chip collection” developed a strong fear based marketing campaign. That campaign warned all small shop woodworkers that inhaling fine dust is very unhealthy, and they offered up their “chip collecting” cyclone with a fine cartridge filter stuffed inside the cyclone outlet as the ideal solution. The woodworking magazines gave this unit high praise, but the newly emerging Internet woodworking forums were a totally different story. Many high end woodworkers are very capable people with a wide range of skills who often have the money to buy top quality equipment. The many of these people who bought this cyclone setup with ducting to protect their health found adding the cyclone made things worse. Those with test meters began doing some testing and suddenly this top magazine rated cyclone vendor was in deep trouble. Their cyclone was a fraud. The filter did not work. Their free ducting design they gave away to entice people to buy their triple the normal priced ducting and cyclones did not work. Their supposedly airfoil impellers were simple very inefficient backward curved impellers. Their filter was a fraction as large as the filter makers said it needed to be to handle the airflows and dust loading. In short the many dozens if not hundreds who fell for that fear based advertising campaign were badly burned, upset, and telling others of their frustration. Instead of fixing their terrible products, that firm used their advertising might to attack and get those who were critical banned from the various forums. Quite a few bright people went to work trying to figure out how to fix these very expensive but dismally performing cyclones.

Larry Adcock was one of the first to recognize that the whole approach of simply downsizing a big commercial cyclone and dragging it indoors was not viable. Larry is a pretty competent fellow who went to work doing the engineering to design a better cyclone. He started with the roughly 40% efficient blower and upgraded to a caged impeller design that is nearly twice as efficient. This let him move more air with a 2 hp motor than most could move with anything less than a 5 hp motor. He then incorporated the neutral vane to decrease performance robbing internal turbulence, and further improved separation efficiency with a helical air baffle better known as an air ramp. This ramp directs the air into a spiral and reduces internal turbulence. Larry opened a small shop and began offering his “WoodSucker” cyclones for sale. WoodSucker soon became the target that other small shop cyclone vendors tried to match. The pricing and performance for the WoodSucker sparked a whole new series of better performers. Larry developed a long backlog on orders with Internet forum posts consistently praising all but the noise and sometimes fit/finish. Larry responded to the few concerns about his units by greatly improving the fit and finish with his WoodSucker II. Owners consistently give that unit very high praise in all areas. Further, it came complete unlike most of the competition that needed filters, hangers, power cords, etc.

My look at this unit showed it built like a tank and a solid performer for a small shop with normal ducting. In looking over the WoodSucker II design and airflow curves, this was the strongest available cyclone for its size motor. Because of its impeller efficiency it was the only 2 hp cyclone I would consider and it was a unit I recommended. I only recommended it for smaller 1-car garage sized shops because even it did not move ample air to handle larger shops. Unfortunately, the same vendor whose dismally performing cyclones inspired the WoodSucker, came back on the attack. As a major advertiser they paid for a magazine to run a just plain bad test. Instead of rating cyclones with real ducting on how well they collected and separated the heavier and fine dust, this magazine test only evaluated on total airflow. It takes a lot of work to force air into a tight separation spiral in a cyclone. As a result, most cyclones use oversized blowers to overcome this high resistance. If you can take away that resistance, then these blowers will move over double the total airflow that they will move when in real use. This upset vendor put absurdly oversized inlets on their cyclones and had their magazine testers do the testing with pipes sized the same as the inlets. With most using 6” diameter ducting, the WoodSucker used a 6” inlet. The resulting testing showed the WoodSucker to be one of the worst performers of all the units tested when in real use with standard ducting it is actually one of the best. Regardless, most do not take the time to really do their homework and tend to believe their magazines. What did not get out is a number of motors burned up from trying to push too much air in the top rated cyclones. Regardless not too long after that dismal review came out WoodSucker stopped answering its telephone and email.

Clear Vue & My Cyclones

I was one of the many who bought and was badly burned by my magazine top rated cyclone. It plugged the filter after every few minutes of use, required taking the cone off to clean the internal filter, and every disassembly left me and my shop buried in dust. Although advertised as a 1200 CFM machine, with the vendor designed and supplied ducting its maximum airflow was well under half the advertised airflow and it measured as little as 90 CFM at the smaller down drops. As a result my ducting constantly plugged in a short vertical main run near the cyclone and the ducting built up huge piles. Frustrated I called the vendor repeatedly until the fellow who claimed to be their senior engineer finally admitted this cyclone which they sold to all small shop woodworkers who only used one tool at a time was gravely undersized and the putting the cartridge filter into the cyclone outlet, an innovation from their president was a nightmare. He told me to rip out the internal filter, replace it with a custom bag his firm was having a third party make for the many disappointed customers, and if that was still not enough I would need to buy a bigger blower or whole new cyclone. After making the filter change, that changed filter design was clearly self destructing from a hard airstream blasting the side of the fitler bag. I was seriously considering a major upgrade.

I did not get that chance because I landed in the hopsital. Allergy testing showed I had become severely allergic to various woods and medical air quality testing on my shop showed my my shop with more than double the airborne dust allowed by OSHA with airborne particle counts thousands of times higher than considered medically safe. My cyclone lacked the airflow to capture most of the fine dust. My vendor failed to tell me my stock hoods were worthless at capturing most of the fine dust. Both the vendor supplied internal cartridge filter and the third party upgrade they had me buy were open sieves that pushed most of the fine dust right through. I spent my months of recovery time gathering suggested upgrades then using the labs at the university where I taught engineering to test and refine the various suggested modifications to make that expensive cyclone viable. I was able to improve airflow by about a third and improve separation by about a third. I shared the results on my Cyclone Modification pages. Eventually I realized that basic design that all still use needed either vented outside or scrapped. With local problems preventing me from venting outside, I needed a better cyclone. The issue is wood gets much of its strength from silica better known as glass. This means fine wood dust is made up of a high amount of ground glass. If a cyclone does not separate off most of this fine dust before it gets to the filter, that filter will soon be history. As the dust accumulates plugging the filter the air pressure climbs enough to force these fine particles to cut and tear their way through the filter. Worse, cleaning just accelerates this filter breakdown, which is why commercial firms use filters with lots of area and clean with fairly gentle shaking.

I started by going back to the basic cyclone physics then came up with a few novel innovations of my own. The cyclone I designed and shared on my web pages rapidly evolved into a very efficient separator which is what cyclones are for. The result worked incredibly well with my university and two other universities rating my cyclone design at 99.9% effective at removing particles sized 5-microns and larger. The closest competition as of the testing done in late 2006 is a cyclone with all the changes from my Cyclone Modifications pages providing 99.9% separation efficiency on particles sized 22-microns and larger. All who have built or bought one of these cyclones of my design swear by them. A few swore at me during the building process because you trade a lot of time for not too much savings. In spite of some grumbling on various Internet woodworking forums, building your own cyclone from my plans or a kit is a very cost effective alternative. If you are patient and have about 20 hours total time, this design offers the best performance available for less than the cost of a good 2 hp dust collector.

After too many complained that building their own from my plans was too difficult I also licensed my design for commercial sale in kit form in trade for a small royalty fee to offset the growing costs of maintaining these web pages. After three attempts to let others build my design did not work out and my health precluded helping my young son to make kits, I moved on. Sadly, a few others without my blessings sell copies of my design without my permission or support, plus most of the vendors now copy portions of my design from my Cyclone Modifications pages. Please do not support these firms as they neither acknowledge my work nor pay me anything for my efforts, plus they send their customers with problems to me for help.

In 2004 Ed Morgano and his son Matt followed the plans on my web pages to build one of my cyclones because they were getting ill from the huge amounts of dust being created by their CNC based MDF routing business that made cabinets. Ed was very pleased at how incredibly well this unit worked after everything else they had tried proved to be nothing but advertising hype. Ed is a retired machinist who specialized in working with plastics. He built another of these units in clear plastic to have a clear view of what was going on inside. He showed off that unit on a few forum pages and was immediately overwhelmed with people asking for him to build them these units. I gave Ed permission to build my design in trade for a small royalty on each unit sold. Although I own no part of this firm, do not manage it, and am not employed by them, I wish I did own a portion of this firm as they have done very well. With just the free small ad on my web pages and making sure each unit is well built and providing excellent customer service Ed and Matt quickly built this Clear Vue Cyclone firm into one of the top suppliers of small shop cyclones. They have done so well that their main competition has gone back to their old tricks putting up falsified performance comparisons on their web pages. Those claims are the same nonsense this vendor has been spouting since their fear based advertising campaign was proven to be a hoax back in the nineties.

Less Viable Options

Although many choose to use smaller dust collectors, small cyclones, and other options, the bottom line is you need to move enough air to capture the fine dust at the source, use good hoods, and then either exhaust the dusty air outside or provide ample filtering. The only other viable options for good fine dust collection must move the required air and provide good filters. The tradeoff becomes how often we have to replace these expensive filters.

Dust Collectors

We found no bag or cartridge type dust collectors in our testing that moved enough air and had ample filtering to provide good fine dust collection and be suitable for indoor use. You can make the larger dust collectors work for good fine dust collection it you put them outside with no air returned to your shop. Most find they need at least the Jet or Delta 1.5 hp portable dust collectors or at least 2 hp dust collectors from other makers to move ample air against the minimal ducting in a small shop. I recommend converting these units that do not come with fine filters to at least a large fine filter bag or preferably a large cartridge filter to get more airflow. Although it is easy enough to make your own cartridge conversion, you can buy retro-fit parts from some vendors or buy a conversion kit from Wynn Environmental that will work on a range of dust collectors that have an 18” to 20" diameter bag tree. I personally modified a Jet dust collector with a Wynn filter because Jet has long had one of the better performing and nicest built hobbyist dust collectors available. Fit and finish have always been excellent, and unlike many who use import motors, Jet has gone that extra mile to provide a top quality motor with all the right qualities to provide years of excellent service including good bearings, heavy duty insulation, and thermal protection. To me buying a cheap dust collector makes little sense because this will be the most heavily used motor in our shops. Unlike far too many, Jet also provides real airflow CFM and filtering numbers that prove accurate under independent testing. Regardless, most find putting the dust collector outside creates emptying problems, plus keeping the filter clean proves too much work, so most eventually shift over to using a cyclone dust collector.

Trashcan Separators

The simplest two stage dust collection system uses a trashcan separator lid and these work well for "chip collection" but poorly for fine dust collection. They can keep wood from beating up your filters and protect your dust collector impeller. I had many years of excellent service from my simple Woodstock (made by Grizzly and sold by many) plastic garbage can lid separator, but did have to seal the hoses and add insulation foam to seal the lid to the trashcan. Sadly, my separator totally failed to work when I upgraded my dust collector and began using larger hoses. With the 4" hoses going to it, it worked fine. When I went to 6" hoses going to 4" just as they entered that unit, it simply emptied my 40-gallon trashcan of all but large blocks. Most others who upgraded their hoses from 4” to 6” and had a 1.5 hp or larger blower found their trashcan separators equally useless. That bigger duct allows so much air to be moved that it simply sucks all out of the trashcan but the heavy blocks. If you read over the theory on drop boxes and swirl tubes, you will find you only need a 5' 1” diameter trash can that stands about 7’ tall to work with an 800 CFM airflow. I’ve done a lot of experimenting with cyclonic separation tops and they work better, but tend to cause even more resistance than a cyclone. Many of us are still working on a viable solution that will work with a high airflow and still be as easy to use and empty as the trashcan.

Small Shop Cyclones

Most small shop cyclones are designs taken from outdoor commercial cyclones that barely move ample air for good “chip collection”, so remain a poor choice to bring indoors with fine filters. The worst cyclones are add-on units that attach to existing dust collection blowers. These add-on cyclones add so much overhead they kill the airflow needed for “chip collection” saying nothing of having no where near the airflow needed for good fine dust collection. The basic cyclone design and engineering for almost all small shop cyclones requires a 2 hp motor for “chip collection” and a 5 hp motor for good fine dust collection. Use of a “neutral vane” and the other changes suggested on my Cyclone Modification web pages can increase efficiency considerably, but not enough for most vendors. Our testing only found one 3 hp cyclone that would actually move the 800 CFM needed in a small shop with minimum overhead resistance. If you toss the indoor fine filters and replace them with big free flow filters with the air directed outside, these make excellent find dust collectors. Otherwise, they just do not provide ample separation, airflow, and filtering for indoor use.

Home-Built Cyclones

There are a number of cyclone plans being sold that are all copies of the same basic “chip collection” cyclone designs. Although recommended for use with fine filters, they units quickly destroy fine filters so at best provide a false sense of security. They also mostly call for tiny blowers that only move enough air for “chip collection”. With the changes on my Cyclone Modification pages and a big enough blower these do make good fine dust collection cyclones again if you direct the air outside instead of trying to filter it amply for returning indoors.

Frequently Asked Questions (FAQs)

Bill, I much appreciate the considerable work you have done to help woodworkers better protect their health, but you have given me far too much. I don't have the time or patience to read through and understand all this. I have just converted over my two-car garage to a shop and just want four simple dust collection questions answered. - Lou

First, many of my family members and friends have all done woodworking for ever and nobody has ever gotten sick. Just how serious is this fine dust problem and is it worth investing the money to provide extra protection for my family and me?

I truly hate answering this question over and over again. Not only have I gone to considerable pain to cover it in more depth than most ever want to hear on my Medical Risks web pages, this question forces me to try and be objective when I really want to just kick some sense into woodworkers who don’t realize they are putting themselves and those close at serious risk. Please re-read the Risk section above.
What are the minimum requirements I should look for in deciding on what dust collection I need? Air engineers did considerable testing and shared over fifteen years of experience of what it takes to address the fine airborne dust problems. They found we must do the following.
1. First, fix our tool ports and hoods so they do not spray the dust away before it can be collected. AAF, one of the better known suppliers of commercial dust collection equipment to facilities that must stay in compliance or can be shut down was kind enough to let me share their many sample tool hood upgrades on my ducting web pages. Those same pages also share various ways to upgrade from the smaller 4” collection ports provided on most machines using better quality laser welded Lindab or Nordfab flanges, or less expensive readily available HVAC flanges.
2. We then must provide ample airflow at each machine for good fine dust collection. Air engineers also established minimum air flow requirements tables for each size and type of tool from careful testing and experience. Since our larger small shop tools are identical to smaller commercial tools we can use this same information. Most of the large commercial tables and all are near exact duplicates of each other. Each of these CFM requirements tables to meet OSHA standards show we must move about 800 CFM at our larger tools and dustier operations. That 800 CFM is not the advertising hype maximum airflow that is about double what a blower actually provides in real use. That 800 CFM is instead what we need to move after taking away the overhead resistance in your shop from your tools, ports, hoods, ducting, separator, filters, etc. Going through the same calculations and testing shows we need 1000 CFM to meet the higher recommended medical air quality standards already adopted in Europe.
3. We must upgrade our ducting to ensure moving ample air. Air engineers long ago established we should target our ducting systems to move air at 4000 FPM velocity to keep the ducts clear without putting on too big of a blower. We can use this 4000 FPM and the 800 CFM airflow requirement in the simple air formula AREA = CFM/FPM to calculate our ideal duct size. A little math shows we need almost exactly 6” ducting to move this much air at the right speed. Ducting size is very important because air at the pressures generated from our small blowers is more like water as it will barely compress at all. Use of the typical 4” and smaller ports or ducting that come with our tools and is available from most woodworking ships is similar to using a water hose that is too small or having a valve partially closed. Any obstruction will serious degrade our airflow. For instance a good 1 hp dust collector blower that can deliver a maximum 800 CFM through a 6” test pipe ends up only delivering about 550 CFM when pulling through a 5” diameter pipe, 350 CFM through a 4”, 200 CFM through a 3” and 90 CFM through a 2” pipe. If we want to move the needed 800 CFM to our larger tools to meet OSHA standards, we then either need blowers that can generate much more pressure or to use all at least 6” diameter pipe from our blowers to our tools. To meet the 1000 CFM needed to meet the higher air quality standards we should use all 7” diameter ducting. If we have a tool that requires two collection points, then we need to make sure that the area of each leg after we split our pipe added together stays very close to the same as our main ducts. A 6” pipe has roughly 28.25 square inches and a 7” pipe has an area of roughly 38.48”. My ducting pages go into far more detail.
  
  Also discussed on those same ducting pages is the importance of ducting design. Sharp angles, rough ducting, obstructions, rough flex hose, bad transitions, tight curves, etc., all seriously reduce airflow. We can use a Static Calculator to determine the total overhead of our ducting and other dust collection components. It only takes a few minutes playing with a static calculator to realize almost all magazine articles and vendor advice on laying out our ducting is dead wrong. Most of this advice was foolishly assumed to be transportable from commercial shops. Ducting does not work that way in small shops because we use tiny blowers that do not generate anywhere near the same pressures or air volumes. Our blowers are sized to barely overcome the resistance of the longest ducting run in our shop coupled to the tool that needs the highest airflow and just collect from one tool running at a time. Using a downscaled version of a commercial ducting design ends up expecting to use a big enough blower to collect from all machines working at the same time. As a result the amount of air moved in a commercial design creates a tree like structure where right next to the blower we need a huge main to carry the airflow going to all the branches. With just one run working at once we instead need to maintain a very close to constant sized duct from the blower right to the machine or we end up with the airflow in the larger mains slowing too much. If that airflow slows too much, the mains build up dangerous ducting dust piles in the larger main pipes. Dust piles can cause ducting fires. When these piles break loose they can ruin our motor bearings, impellers and filters. Moreover, when they break loose they can create a potentially explosive dust to air mixtures. In small shops with a single point of collection we need to use nearly the same sized ducting throughout. Most end up needing at least 6” diameter mains and down drops whose area added together ends up matching the roughly 28.25 square inches of our 6” mains.
4. Air engineers then tell us to either send the air outside or filter it. They always recommend sending the air outside and using radiant heaters to keep from having bad heat losses. They found that keeping the air inside and trying to filter it is a nightmare. First, filters need to comply with some standard and that standard ranges from wide open just blowing all the fine dust right through to filtering at 0.1-micron or better. Current cyclone makers would like us to believe that filtering to somewhere around 10-microns is ample. As discussed before, the medical experts would like us to provide at least 0.1-micron filtering as is now the European standard. I found it difficult and expensive to get 0.5-micron filters. Moreover, as the fineness of our filters increases, we have to either provide much better pre-separation or significantly more filter area.
I fully expect to follow the footsteps of my father and grandfather starting my woodworking hobby modestly with a good set of hand tools then as I get more proficient adding a few stationary tools in the basement, and eventually building a dedicated shop. I suspect most go through a similar progression. How should I manage the fine dust during the growth of my hobby? For new woodworkers I recommend starting woodworking as a fair weather activity where we work outside wearing a good certified NIOSH dual removable cartridge mask when making fine dust. I use a 3M half mask in my size from a local hardware store that stocks a range of filters allowing me to also use this mask when painting and spraying my garden. This lets us get going without a huge cost in tools or putting our health at risk. The basic tools will be useful around the home even if woodworking turns out to not be a long term hobby. I now personally do quite a bit of my work outside using a good hand held power saw, router, jig saw, drill, orbital sander, and oscillating spindle sander with a guide system instead of my large stationary power tools. I find I can do all just as well, with far less setup, and considerably more ease especially when working with large sheet goods. Festool probably makes the nicest of these type systems and other vendors offer a range of similar offerings. I personally use the Eureka Zone EZ-Smart guide system and table. This system is so versatile my daughter and I made her a nice desk in the fall of 2005 without doing any machining or sanding indoors.

Most work indoors and end up getting at least two dust collectors before upgrading to a cyclone system. If you have a garage attached to your home or worse, a basement workshop like yours, then I strongly recommend skipping this step and going straight to a good cyclone based system. I also recommend use of radiant heaters in your shop and blowing the dust away outside ensuring that you provide ample make up air to keep from drawing deadly carbon monoxide backward through your vents, stoves, and fired appliances.
And finally, like most I am supporting a family, so have serious financial constraints on my woodworking expenditures. I also want to end up with good quality equipment that will last. How do I manage this dust safely without breaking the bank and will you recommend specific brands and models for each phase of this adventure? If you will not work outside, I still suggest you buy or make a cyclone that you vent outside. The cost to build your own is about the same as a typical dust collector ample for your sized shop, and will save you having to go through the two or more dust collectors that most of us have to buy before waking up. I personally kept my Jet 1.5 hp dust collector because it is a well built unit and with my DC Cartridge Conversion works great for quick jobs where I don’t want to turn on the cyclone. At the same time, I know this unit pumps too much dust into the filter that I need to change that filter frequently to keep myself protected.
Bill, I have a small 2-car garage sized shop with no ducting, what dust collector should I buy? I don’t recommend buying any dust collector, but if you have to please ensure it moves enough air for good fine dust collection, that you use ducting to put that unit outside where the fine dust cannot blow back indoors, and that you use fine open filters that flow the most air to provide the best collection. Also, be aware that many vendors either lie or advertise exaggerated airflows. The best two 1.5 hp dust collectors are made by Jet and Delta, yet neither of these generates ample pressure to overcome the normal resistance to power the ducting in your two-car garage sized shop plus the resistance of your dust collector filter. Your shop needs one of the better quality 2 hp or larger dust collectors to provide ample airflow. One caution here, please don’t get sucked in by false advertising that offers 2 hp and larger dust collectors that plug into a standard 120V plug. Some vendors play games rating their motors based on starting amperage instead of working amperage so call 1.5 hp and smaller motors 2 hp to as much as 6.75 hp.
Bill, you have me confused again. You say we need 800 CFM in one place as a minimum yet in other places recommend at least 1000 CFM at our larger tools and dustier woodworking operations. How much CFM do you recommend? Air engineers have spent over fifteen years refining their tables that show the minimum airflow needed to provide the collection at different tools ample to meet OSHA air quality requirements. Since most large hobbyist tools are identical to smaller commercial tools, we can use these same tables. CFM requirements tables for our tools to meet the medical air quality requirements already in use in Europe are not yet available, but the testing shows we either need tools built from the ground up to totally contain the dust as it is made or that we need about 1000 CFM at most larger hobbyist tools and dustier operations. In general, if you add about 25% to the existing CFM requirements tables you will get fairly good CFM numbers to meet the higher standards.
What cyclone do you recommend? In six years of testing I never saw a single small shop cyclone other than the WoodSucker II and the Clear Vue Cyclone using my design that provides good enough separation to be used indoors with filters. Although there is again considerable advertising hype where vendors test their cyclones against heavy chips and make outrageous separation claims, all other small shop cyclones are downscaled copies of the early outdoor commercial “chip collecting” cyclones. These 5 to 12.5 hp cyclones were engineered long before the current fine dust standards went into place. They do an excellent job of “chip collection” and use wide open filters engineered to pass all the fine dust into the outside air where it just blows away. This means they blow the 30-micron and smaller particles that make up almost all of airborne dust right through. With these units placed outdoors to meet fire and building safety codes, their only real problem is being built to only move the 350 to 450 CFM needed for good “chip collection”. To make one move that airflow for good fine dust collection they typically need just about twice the blower size. Instead, small shop vendors sell them with blowers smaller than half the original size where a 5 hp cyclone was only considered ample to collect from one or two machines at once. Worse, ignoring commercial fire and building codes to bring these indoors with either too open or undersized filters creates a nightmare of dangerously unhealthy fine dust exposures where many will follow my lead and eventually get ill because these units are dust pumps. In short, either build your cyclone from my plans, buy one from Clear Vue Cyclones, or buy one of the larger at least 3 hp cyclones and toss the filters and direct the air outside.
You confused me with your blower fan tables. On one hand you recommend use of a 5 hp motor to power your cyclone, but the fan table says I need 7.5 hp and you say elsewhere that I can get by in my average sized shop with a 3 hp cyclone. How much motor do I really need for my cyclone? How about I answer this question with a question, how big enough of a motor is needed to power my car? The answer is the same it depends upon the size of car and its use. A typical chip collection cyclone that is a copy of the original Delta outdoor cyclones that most vendors copy needs roughly a 5 hp motor. Even with all the changes suggested on my Cyclone Modifications web page that many vendors have copied often without giving credit for this work, the best resulting cyclone still shoves more than half the overall airborne dust into the filters. This quickly kills filters making these units in my opinion inappropriate for indoor use with filters, so I only recommend their use if you blow the air directly outside with no filter. Dropping the overhead resistance of your filter makes these units able to support collection from one large machine in a typical two car garage average sized shop with just barely a 3 hp motor. Unfortunately, because many small shop blowers are so sloppily built, they generate considerably less than commercial blower air flows, so many 3 hp small shop blowers will be undersized. More, cyclone vendors oversize impellers to compensate for the high resistance of our cyclones and ducting. Otherwise the impeller would just turn doing minimum work because it becomes air starved and cannot get the air it needs. Using a bigger impeller generates more pressure and lets us move more air. We carefully balance motor size, impeller size and resistance to provide maximum airflow without working our motors beyond their rated amperage. What may be a perfect balance for your longest ducting run and biggest tool can be a disaster for your motor when collecting from a close machine with minimal resistance. The motor can try to push more air than it has rated amps to move. This soon burns up motors. That is why I recommend use of a 5 hp motor on my cyclone design that works great with a high resistance long run. It really needs only a 4 hp motor to ensure motors don’t burn out, but because motors come in 3 and 5 hp, not 4 hp, I bumped up the impeller size from 14” to 15” in diameter to use that extra horsepower without putting the motors at risk. The result is higher pressure and the increased airflow to ensure meeting the airflows needed for collecting the fine dust at the finer standards now being adopted.
Perhaps the most popular dust collector available today is the very inexpensive Harbor Freight 2 hp dust collector. Can I use one of these sitting outside my shop for good fine dust collection? Can I later use this same motor and blower to power a cyclone? When that dust collector first came out I tested it thoroughly, did a long write-up on it that was shared out on a number of Internet sites, and then upgraded those write ups a number of times as this unit evolved. It started as a piece of junk with innumerable initial failures, but Harbor Freight made good on the units that failed and fixed the many problems. That still leaves this as a real roughly 1.6 hp dust collector that moves about the same airflow as many of the 1.5 hp units. I found it marginally lacking in total airflow for good fine dust collection as a dust collector and severely lacking in power to meet the much higher demands of a cyclone. Doing a fine filter upgrade as recommended on my DC Cartridge Conversion page raises the airflow amply for it to be a good unit to use outside a small to medium sized shop.
Bill, you have me really confused and seeing things. I read over both the American Woodworker and Wood Magazine cyclone reviews and just about every cyclone they tested goes well over the 800 CFM that you require. They also generate far more pressure with a 2 hp motor than you say is needed for a 2-car garage sized shop with ducting. They clearly label the ducting overhead on one of the charts. Do you agree they move enough airflow, and if not why not? This is one of those questions that does not make my day. If you look at a good fan table it will tell you how many horsepower it takes to move a given airflow at a given level of pressure. Without going through the steps figure 2.3" resistance at the tool, another at least 3.5” for a good cyclone, 0.5” more for big fine filter, then another at least 1.6” resistance for the ducting in a small shop for a total of at least 8” for an average 2-car garage sized shop. After testing untold many small shop blowers, I still have to find my first that actually provides more airflow than the commercial blowers. Most provide considerably less. Looking down a typical commercial blower fan table column for 8” of resistance it shows a 2 hp motor will not ever have enough hp to move our needed 800 CFM. Checking down the 7" resistance level column we see it will just barely move our 800 CFM at 7” of resistance. At 8” we can’t get the job done. Even with too little airflow for good fine dust collection, this 12” impeller with a 2 hp motor causes another more serious problem. Look at what happens when we hook this same cyclone up to a big tool right next to the cyclone with no or minimal ducting. What happens is the airflow climbs significantly as does the hp demand which goes to 2.5 hp. That will burn up a 2 hp motor pretty quickly.

We adjust for pressure by using bigger impellers and bigger motors because our direct drive motors are fixed speed. Many small shop vendors now advertise their cyclones with 14” impellers, a 7” inlet, and only 2 or 3 hp motors. Looking at the same fan table says a 14” impeller can move a whopping 1377 CFM airflow at 8” but to do so it is drawing a real 3.77 hp. Neither a 2 nor a 3 hp motor will stand that kind of load for long. If as before we look at the minimum load from collecting from a big tool right next to the cyclone with minimal or no ducting this same sized impeller draws an even bigger 1649 CFM at 4.58 hp. That load will soon burn up either a 2 or 3 hp motor, but until it happens oh do these look good. So then the next question is how to they make them work with 2 and 3 hp motors and not burn out the motors all the time. The answer is the same. These blowers are far less efficient than commercial blowers so the design problems, poor manufacturing, and use with restrictive ducting saves lots of motors. It also makes for some pretty dismally poor test results. We do not get more airflow for nothing.
What makes your cyclone design a better choice than the many other offerings? Four things cost, airflow, separation efficiency, and overall resistance. You can build one from my plans and pay me little to nothing, or buy one from Clear Vue Cyclones with a 5 hp top quality motor for less than most other vendors charge for their 3 hp units with lesser quality import motors. Most small shop cyclones are built to provide the typical "chip collection" airflows of about 350 CFM. The bigger 5 hp cyclones provide a real airflow of about 800 CFM needed at our larger tools to provide fine dust collection ample to meet OSHA air quality standards. My cyclone design is engineered to provide a real 1000 CFM at our larger tools to provide the airflow needed to meet the medical recommended air quality standards that are 50 times more strict than OSHA and already the European standard. The cyclone separation has a real separation efficiency instead of some fabricated efficiency made up in the back advertising rooms. In hard numbers my cyclone on standard test dust that matches the OSHA standard of 30% fine airborne dust my cyclone design provides an overall separation efficiency of over 99.7% separation efficiency by weight. This gives a real fine dust separation efficiency of about 98% versus a typical neutral vane equipped cyclone at less than 44%. Since this fine dust plugs and destroys expensive filters, this separation efficiency saves both our health and pocketbooks. I have people who make two to three hundred pounds of fine MDF dust a day using my cyclone for six months or more before they need to clean their filters. My prior "best" cyclone allowed less than twenty minutes of routing MDF before I had to stop and clean the filters. Finally, my cyclone design has far less resistance than most other units so the horsepower of your blower motor goes into separation efficiency instead of getting wasted overcoming cyclone overhead. The combination lets you provide good fine dust collection airflow and separation before filtering that are far beyond OSHA, ACGIH, and approaching medically recommended standards today instead of struggling with equipment that mostly will not meet the OSHA standards that most have already abandoned because these air quality levels leave too many getting ill.
What do you have to say about the current top magazine rated cyclones and best selling cyclones? Do you recommend any of these? I think the original Delta 5 hp chip collection cyclone that most small shop vendors copy to one degree or another is probably the top selling unit and if you count all the clones it has been the top selling for many years. I think this is a great cyclone if you put a big enough blower on it and direct the air outside exactly as the cyclone was designed. I am not at all in favor of any of the copies with tiny motors, blowers, and filters. They lack the airflow, separation needed to protect the filters, and ample filter fineness and sizing to make good fine dust collectors.

In terms of magazine ratings I have spent countless hours helping to educate magazine authors and editors to improve their testing protocol for cyclones and dust collectors. Future tests should look at the important things like separation efficiency, resistance, airflow at typical shop resistance levels, and provided filtering. Hopefully these many long discussions have weaned them away from this fallacy that “best” is the one that moves the most airflow claiming the highest CFM. I can change test pipes and make just about any unit I want appear to be a “maximum airflow” winner. Far more important is will each unit provide the airflow needed for “chip collection” or good fine dust collection with the size ducting at the resistance levels typical for each sized shop. Best is the unit that best protects our health with enough airflow to collect the fine dust as it is made, enough power and air pressure to overcome the resistance of our normal ducting, and then the ability to safely get rid of that dust.

When I go looking for a vendor I want one I can trust. I don't trust any of the top rated cyclone makers because there has been too many years of funny business with bogus health claims, exaggerated airflows, falsified separation efficiencies, and dangerous filtering claims. I do know a few of the better known vendors continue to be in a very open and ugly public fight on their web pages and Internet woodworking forums leaving me feeling their bottom line is different than my interest in helping to protect the health of woodworkers. I have had so many pieces of hate email against all of these small shop cyclone makers except Jet and Delta that I hope to never receive another. These concerns sadden me but are not much of a surprise. In spite of my prior negative experiences I still chose to do my best to help all improve their cyclones. Many have lifted my advice then claimed it as their own. Frankly, I have no need, want or desire to comment further. The only public recommendation I will make is their 3 hp cyclones work pretty well for average sized shops if you toss the filters and exhaust the air directly outside. I would not consider any of them appropriate to use with indoor filters.

Home

Table of Contents

Summary

Foreword