This blog defines and shares the dangers of fine dust then provides an overview of what it takes to get good fine dust protection. It targets woodworkers but applies to all who work in dusty air such as those who work with stone, sand blasting, finishing, fiberglass, etc. It also explains the difference between chip collection and fine dust collection.
Most are confused by small shop dust collection. Chip collection collects the dust and chips to keep our tools, work surfaces and floors clear of the dust that can lead to people falling, accidents, fires, and poor quality work because the dust obscures the work. Chip collection has been a requirement in many areas since the 1920s, so is well understood and what is required for good chip collection is well documented. The confusion is caused because most small shop vendors add a finer filter to their chip collectors then advertise the result as a good fine dust collector.
Fine dust collection collects amply to keep the airborne invisible unhealthiest particles down to a safe level. Most wrongly assume that a dust collector that can suck up a block of wood or heavy tool should do a great job pulling in fine dust that can be moved with the lightest breath. We already know from using our vacuums that we only can pick up right next to the nozzle. This is because sucked air comes from all directions at once so air speed drops off at roughly twelve times the distance squared. Decades of experience and research show we need about three times normal chip collection air volumes to get enough speed to collect the fine dust before normal room air currents blow the fine dust all over. So adding a finer filter to chip collection equipment with only one third the needed airflow does not provide good fine dust collection, especially when woodworking because woodworking generates so much fine invisible dust compared to how little it takes to harm our health. Since wood dusts don't breakdown until they get wet and most shops foolishly don't vent outside, the fugitive dust that escapes collection builds so much that in most small shops just walking around stirs enough fine dust airborne to fail air quality tests without doing any woodworking. This blog helps share what small shop owners can do to better protect themselves with much better fine dust collection.
After a lifetime of teaching university engineering and woodworking I had a healthy respect for fine dust and it still badly blindsided me. When making dust I always followed what is still the safest advice. Always put on a good NIOSH certified dual cartridge respirator mask and turn on a strong fan that moves fresh air through our shops. The mask and fan should go on before we start making dust and stay on for about a half hour after we finish making dust. Remember, even a razor sharp plane that makes no visible dust launches millions of invisible unhealthy particles. Tired of freezing during the cold months and burning up during the hot months working in the third bay of our garage where we also park two cars, I wanted a better system for when I retired and could do more woodworking. In 1994 I built a kit cyclone. It and the following kit cyclone I built worked so poorly I spent a lot of time making and documenting my improvements amply that now few small shop cyclones don't use some of the innovations I shared. Still, none were enough. After wasting too too much time on dust collection I stupidly threw money at the problem. I installed the top small shop magazine rated cyclone dust collection system advertised to provide good health protection and provide ample airflow to collect from three large and one small tool working at once. I used the vendor supplied ducting plan to install the vendor supplied ducting and upgraded to their best fine filter. This system left me spending more time clearing its clogged its cyclone cone and fine filter than doing woodworking which left me and my shop covered in the dust I bought this unit to avoid. It also collected so poorly that soon after installing this system I decided to junk it and buy a commercial system. Thinking it at least protected my health I foolishly used it for another few weeks only to get rushed to the hospital with an apparent heart attack.
My doctors found a bad allergic reaction to wood dust left my lungs unable to supply enough oxygen to my heart. I refused to believe this because I had just had a recent allergy test that showed no problems, plus used the best small shop dust collection system with finest filters available. I also had continued to wear my fitted dual cartridge respirator mask when doing dusty work because no dust collection system can capture all the fine dust. Allergy tests confirmed with nasty welts and boils severe allergic reactions to a wide range of woods, many of which I never used. In just a few months I went from no allergy problems to such bad allergies that my lungs would not supply enough oxygen for my heart. My respiratory doctor a fellow woodworker, said he has seen many develop severe allergies to cocobolo and rosewood in as little as a few hours exposure.
Testing / Education
My health did not improve and the allergic reactions continued so my respiratory doctor felt I had contaminated my home, He convinced me to pay for expensive air quality testing. My certified inspector gave me quite an education and shared the detail of what the major vendors found it takes for good fine dust collection, as follows.
Inspection: My inspector was the senior OSHA inspector for our area who has tested hundreds if not thousands of shops. He said my shop was one of the cleanest he had ever seen, but my new cyclone system would badly fail all the way around. I did not believe him as no woodworking had been done in my shop for three months and during that time our cars that share the garage were constantly going in and out, so it had to be well cleaned out. Just walking around without doing any woodworking stirred up enough invisible dust to cause my shop to fail its air quality test. His gauges showed as soon as we turned on my cyclone my filter was a dust store that blew so much fine dust all over the air quality got five times worse without any woodworking. My system worked so poorly a few minutes of woodworking pushed the airborne dust level as high as normal room air can carry. He said the fugitive dust that escapes collection builds so much that most small shop workers and hobbyists who vent inside get more fine dust exposure in two hours than most large facility commercial workers get in months of full time work. His meters showed my home badly contaminated and a chemical test showed the main contaminate was wood dust. He explained fine invisible dust is so light it behaves more like an odor to rapidly contaminate any shared air space. Worse, wood dust lasts nearly forever unless it gets wet. Going through the door that connects my garage shop to my home let the contaminated air into my home, plus I carried lots of fine dust in on my hair, skin and clothes. His test gear showed even my fine home air filters freely passed the fine wood dust, so the contamination just continued to build with whatever came in from my shop.
Proper Design: My inspector said my vendor's advertising claims promising good fine dust collection from three large tools and one small tool working at once are nonsense. He said he tested many shops with this vendor's dust collection systems and none passed air quality tests. He explained that this vendor's design failed to do most of the things that the major vendors who guarantee customer air quality have long shared as needed for good fine dust collection. They also ignored the National Fire Protection Association safety rules that are building codes in most communities. The vendors who guarantee customer air quality found the only way to get good fine dust collection is to collect the fine dust at each source as it is made. The problem is woodworking makes so much fine airborne dust and it spreads so rapidly that there is no chance that air cleaners and exhaust fans will get rid of enough airborne dust fast enough to avoid failing an air quality tests. As shared his particle counter had already proved him right as my shop and home were both badly contaminated.
Fire Safety: He said my dust collection system would fail building, fire marshal and home insurance inspections because my system was placed inside and not certified as fire and explosion proof, plus its cardboard collection bin was a fire just waiting to happen as were the plastic bag below my older dust collector and plastic tub below my shop vacuum. He shared that most shop fires occur because a spark gets into the collection bin then smolders to later grow into a fire, often long after we have left our shops. To be legal all had to be put outside behind a fire and explosion proof barrier.
Proper Hoods: He said most dust collectors are optimized to move air at 4000 feet per minute (FPM) which is a little over 40 miles per hour. Most of our blades, bits, cutters, and sandpaper launch fine dust filled air streams at over 100 miles an hour, so we must start with upgraded hoods that contain, direct and enable capturing the fast moving air streams or there is no hope of good fine dust collection. None of my tools had the upgraded hoods required.
Ample Airflow: He said that chip collection which collects the same visible sawdust and chips that we would otherwise sweep up with a broom has been a requirement in some areas since the 1920s, so is well understood. It takes a real airflow at most small shop stationary tools of 350 cubic feet per minute (CFM) to provide good chip collection. Good fine dust collection has been a requirement in some areas since the 1960s so is also well understood. Good fine dust collection at the same stationary tools that get good chip collection with 350 CFM need a full 1000 CFM to pull in the fine dust. We already know why. Fine light dust that can be blown around with the least breath will get blown all over our shops unless we move enough air to surround the working areas of our tools with enough suction to pull in this fine dust before it gets blown all over by normal room air currents.
Ample Blower: He also shared that my cyclone blower was far too small. Blower technology is mature meaning if we buy the same type, size, and speed of blower from any of the major blower makers the performance will be near identical. This lets us use blower tables that let us see how much air a particular blower will move against different levels of resistance known as static pressure. These tables show that dust collection blowers need at least 3 hp to move the 1000 CFM needed for good fine dust collection when using a dust collector and at least 5 hp when working with cyclones as they take more overhead to force the air into a tight separation spiral. Sadly, most small shop blowers are not nearly as well made, so these blower tables show higher performance than most get from their small shop dust collectors and cyclones. My vendor's cyclone used a much smaller than 5 hp blower so there was no chance that it could move enough air to provide good fine dust collection. His test gauges showed even when collecting from just one tool working at a time the airflows my system provided ranged from only 30 CFM to a maximum of less than 350 CFM irrespective of my vendors 1200 CFM claim. It moved far less when trying to collect from more than one tool at a time. Clearly my blower was too small to move enough air for good fine dust collection.
Ample Ducting: After looking at my ducting my inspector asked if I was having problems with piles building in the main ducts. My inspector explained that the graduated ducting in my shop that went from a 7" main to as small as 1" diameter down drops was impressive looking but dead wrong for a small shop. He explained that air at dust collection pressures is like water in that it does not compress so any small or undersized duct or small tool port acts just like a partially closed water valve and severely limits airflow. This means for a large shop with no blast gates the duct size must increase with each branch through the main ample to carry the larger amounts of air. That makes for a very impressive look, but in a small shop with a blower only large enough to collect from just one machine running at a time, all ducts and down drops should be the same size or just slightly larger for the horizontal main and blast gates are required to enable collecting from just one machine running at a time. My system came with 1", 2" and 3" sized down drops, but any down drop smaller than 4" will not carry even the 350 CFM needed for good chip collection. He said in addition to terrible dust collection, these undersized down drops were very dangerous because they restricted the flow so much there was not enough airspeed to keep vertical runs from plugging or prevent building piles in the horizontal runs, particularly mains. He explained this dismal airflow is why my ducts kept plugging and building up huge piles. He said ducting piles are very dangerous as any spark can quickly get blown into a nasty ducting fire. When these piles break loose they create one of the few times in small shop woodworking where we have a potentially explosive dust to air mixture.
Dust Riddance: He said most choose to vent outside instead of filtering because filters constantly need cleaned, are expensive, typically need replaced every three months, and venting inside gets rid of the fine invisible unhealthiest fugitive dust that escapes collection instead of letting it build to dangerously high levels. He asked if my filter clogged constantly. When I said yes he explained this was because it was far too small. The filter makers recommend a minimum of one square foot of fine filter area for every four cubic feet of air and for maximum filter life and less cleaning they recommend using at least one square foot of fine filter for every two cubic feet of air. My system which supposedly moved over 1200 CFM had about ninety square feet of filter area, roughly one sixth as much as recommended and less than one third the minimum. He said the filter area problem was bad is big problem with my shop was because I vented inside which guarantees my shop would badly fail its air quality checks just from the buildup of residual dust in my shop.
Unsafe Impeller: I later learned the National Fire Protection Association (NFPA) that writes building inspector and fire marshal standards now strongly opposes use of aluminum impellers in dust collection systems as came with my cyclone. All dust collectors and cyclones with full bins put all right through the blower impeller. When an aluminum impeller gets hit by a piece of metal tiny slivers of aluminum come off aluminum impellers that can burst into dangerously white hot flames. Burning aluminum is known as a thermite reaction and is exactly how 4th of July sparklers work. My vendor who continues to boast of their custom designed aluminum impellers forgets to mention this real risk.
Overall: Calling in a pro showed this expensive system I installed to protect my health was a dangerous dust pump that created a bad false sense of security leaving a clean looking shop while it produced dangerously high invisible dust levels. This inspired me to spent my recovery time figuring out what happened and coming up with solutions to protect my family and me. My respiratory doctor was so impressed with my solutions he talked me into sharing leading to my Cyclone and Dust Collection Research web pages. Daily thousands read my web pages and over 10,000 people worldwide use cyclones of my design to help with their dust collection problems. I was asked to build this blog as a quick way to get out the basic information. The following shares more detail from those pages.
Fine Dust Definition
The picture here shows the different sized particles compared to an average human hair which is about 70-microns thick. For reference there are one million microns in a meter which is about thirty nine inches long. Airborne dust particles are sized under 30-microns. The unhealthiest fine dust are the airborne dust particles sized under 10-microns known my medical people as inhalable dust because it gets by our natural protections. Researchers so extensively study fine particles they use a shorthand to name the particles. They call airborne dust PM30 meaning particle material (PM) sized under 30-microns and fine inhalable dust PM10 meaning particle material smaller than 10-microns.
Fine Dust Sources
Most small shop activities generate huge amounts of fine airborne dust particles. Activities that make any smoke are particularly bad, especially woodworking. When viewed by an electron microscope we see wood looks like a big bunch of glued together tubes. Wood gets much of its strength from silica better known as glass. Every time our blades, bits, cutters and especially sand paper touch wood they shatter these fragile tubes launching millions and millions of tiny dust particles airborne. An engineer friend said at a microscopic level working wood is similar to working a stack of glass tubes with a rock ax. Particle meters show even the sharpest hand plane that makes no visible dust launches millions of fine invisible particles as the blade smashes through wood.
As part of my ongoing research my professor and engineer friends tested hundreds of shops. Almost all shops vented their traditional chip collection technology inside which either the shop owner or equipment vendor had added finer filters. All but two had built up so much fine dust they failed their EPA air quality tests by just walking around or turning on the dust collector or air cleaner without doing any woodworking. The only reason those two passed is both shop owners worked with a strong fan blowing the air through their shops. Our particle counters showed almost all used stationary tools with hoods that sprayed huge amounts of fine dust all over. Our air meters showed almost all used way undersized shop vacuums, small dust collectors, or small cyclones that moved far less than the air needed for good fine dust collection. And, almost all shops used 4" diameter ducting that limited airflow to under one third what was required for good fine dust collection. Making things worse, almost all shop vacuums, dust collectors, cyclones, and air cleaners that claimed coming with fine filters did not. Our testing showed when new all small shop fine filters freely passed 10-micron and smaller particles. In short, most small shops were just like mine and had serious dust problems.
We learned most of our vendors sell equipment not based on how well it works, but instead on what it takes to be cost competitive. There are no standards or oversight on small shop equipment makers except what we choose to buy. Making informed choices is tough because most available advertising information is misleading. Our truth in advertising laws permit vendors to say anything they can prove for an instant. For instance I can claim my car gets 99.9 miles per gallon because my mileage gauge shows this reading when coasting down a steep hill. With filters so long as the vendor does not include flow, they can claim anything they want. Even a chicken wire screen with 1” openings when clogged enough will eventually become a 0.3-micron filter but will have little to no airflow. This is why ASHRAE who sets the filter standards requires that all indoor filters be tested when clean and new and measure both airflow and filtering.
Fine Dust Lifetime
My inspector said most small shop dust problems come not just from the dust we make while doing woodworking, but more from dust we made during prior woodworking. He explained that wood dust lasts until it gets wet. In fact, when one of the pyramids was opened they found considerable fine wood dust. One reason that wood dust lasts so long is wood gets most of its strength from silica better known as glass. As the soft organic portions of the wood cells break down what is left are glass shells embedded in very tough lignin fibers.
Fine Dust Behavior
Fine invisible dust particles are so small and light that normal room air currents are enough to keep them airborne. Fine dust behaves like a bad odor. These fine light particles quickly spread to evenly fill all available air. Think about working with a skunk in your shop. If your shop is in your garage like mine, just opening the door can contaminate your home.
So, for those who vent inside unless we regularly blow out our shops the fine dust just keeps building and building. Just about any air movement will stir the residual dust back airborne again and again. Many report that their logging particle meters running at night show their dogs and cats going through their clean looking garage based shops stir up enough fine dust to create unhealthy air quality.
Fine Dust Health Risks
All airborne dusts are unhealthy because they cause irritation that if continued can result in infection or worse. If you want to be totally overwhelmed do a Google search on PM health risks. This will give millions of references that shows the worst airborne dusts are fine dust particles also known by medical people as inhalable particles, meaning PM10 particles that are so small they are invisible without magnification and they get right by our natural protections. Based on particle size these fine invisible particles lodge stuck in different portions of our respiratory systems where their sharp edges and sharp often barbed points damage and scar our tissues. Worse, fine dust exposures are particularly dangerous because we generally don't notice any damage as it occurs but the resulting damage builds over time. The credible medical information says the following. The peer reviewed medical research shows every fine dust exposure of any type dust causes a measurable loss in respiratory capacity, some of this loss becomes permanent, and the more and longer the exposure the worse the damage. This damage over time is so bad that the EPA, European Union, and medical experts set very tough limits on fine airborne dust. Most only permit 0.1 milligrams per cubic meter of air which is near nothing compared to how much fine dust most shop operations create.
Wood Dust Health Risks
All fine airborne dusts are unhealthy, but wood dust is particularly bad. As shown in this electron microscope picture wood particles have razor sharp edges and sharp often barbed points that damage and scar our respiratory tissues similar to asbestos and lock this dust trapped lodged deep inside our lungs where our bodies have a very tough time getting rid it. The damage from fine dusts of any type are so bad that the EPA only allows airborne fine dust levels below 0.1 milligram per cubic meter.
Wood dusts also carry toxic chemicals that can cause serious short and long term problems. The toxic chemicals found in and on wood can cause irritation, inflammation, respiratory problems, asthma, emphysema, worsening allergic reactions, poisoning, nerve damage, and even increase our risk of cancer. Many woods such as mimosa, yew, and oleander are so poisonous they can kill us. Most woods contain chemicals that can eventually cause allergic reactions, but a few woods such as cocobolo, rosewood, and walnut are so toxic they can cause us to build a nasty allergic reaction in just a few hours exposure. Always check a good wood toxicity table before working any wood then amply protect yourself. These fine particle damage and toxic chemicals often combine with other elderly health problems to significantly reduce our lifespans.
Large commercial facilities almost all vent their dust collection systems outside, so these firms rarely have any significant build up of fine dust. In 2000 when I first started doing research, the large health care insurance firms shared their data on-line. That data vanished when people started using it to sue insurance firms, particularly over asbestos fine particle respiratory damage. Their data showed at typical large facility exposure levels where the fine dust is vented outside, one in seven workers develops such bad wood dust allergies they must stop woodworking. One in fourteen ends up being forced into an early wood dust triggered medical retirement. Almost all lose about 1% of their respiratory capacity per year of woodworking. Most built such a significant loss in overall respiratory capacity that it ends up worsening other age related illnesses. Average life expectancy fell roughly ten years.
Wood Dust Volumes
Wood dust volumes are huge compared to how little it takes to harm our health or fail an air quality check. An average two-car garage sized shop contains less than 100 cubic meters of air. All types of fine dust are so unhealthy that the EPA indoor air quality maximum is only 0.1 milligrams per cubic meter. Multiply our 100 cubic meters of air in an average shop times the 0.1 milligram EPA limit and we see that a typical two-car garage sized shop will fail an EPA air quality test as soon as 10 milligrams of fine dust goes airborne. This is only a tiny thimbleful of dust and less fine dust than we get from slapping a dusty shop apron or hand sawing just over seven inches of 3/4 inch wood. OSHA testing shows with every twenty pounds of sawdust woodworking makes on average 5 1/3 ounces of fine dust particles which is 151,191 milligrams. This means every twenty pounds of sawdust makes enough fine dust to cause 15,119 average two-car garage sized shops to fail an EPA air quality test. Even with a 99% effective dust collection system we still spread enough fine dust in our shops to cause 151 typical shops to fail an EPA air quality test. Because wood dust lasts nearly forever unless it gets wet, most shops that vent inside build up such dangerously high amounts of fine invisible dust that just walking around without doing any woodworking will launch enough fine dust airborne to fail air quality tests. Clearly most small shop activities make huge amounts of very unhealthy fine invisible dust compared to how little it takes to cause serious health problems.
A risk analysis compares how bad things can be against the chances of that happening then tries to make a measured response. Unless you are the one in seven who develops an allergy, you get poisoned or develop cancer, the odds are you will never be aware of or inconvenienced by the long term damage caused by wood dust until your later years. Because this damage builds and the amount of damage depends on exposure levels, this should terrify small shop workers and hobbyists because our exposures are hundreds if not thousands of times higher from venting inside than workers in commercial shops who vent outside. The medical research clearly shows the more dust we take in the greater the damage. Most have poor systems that either miss collecting the fine dust or blow it right through too open filters. My shop was better than most shops we tested. My shop was tested three months after I stopped doing any woodworking and the dust levels in my shop were so high that a couple of hours in my shop generated more exposure than commercial woodworkers get in months of full time work. At these exposure risks all should do our best to protect ourselves from too much fine dust exposure. The most certain and least expensive protection is wear a good NIOSH dual cartridge filtered respirator mask and use a strong fan blowing out a back door or window with a main door open a bit. We can minimize our exposure by also having good fine dust collection but this is much more work.
Recommended Minimum Protections
- Always wear a mask whenever you make fine dust and continue to wear that mask until your shop is well blown out. I recommend the 3M 7500 series masks fit properly to not leak. I personally also use the 3M organic vapor cartridges with their special pre-filters. You should keep your organic filters (or whole mask) in a zip lock freezer back that you suck all the air out of before sealing. This slows the activated charcoal in the filters from getting worn out.
- The best way to keep your shop cleaned out of the fine dust is to always work with a good industrial 30” or bigger fan in a side door or window with an opposite door or window open when you are making fine dust. Always run that fan for another 30 minutes after you finish making fine dust. My test meters showed most need thirty minutes for the shop air to get cleared back to outside levels. This keeps the fine invisible dust from building and creating a bad residual dust problem.
- Because we cannot avoid making some fine dust with our tools, I recommend those that work in shops or garages that attach to our homes also install a simple bathroom vent that comes on when we turn on the light. This creates a low pressure that keeps the dusty air from rushing into our homes whenever we open a connecting door to our homes.
- Avoid tracking dust into your home, office and vehicle. Always wear a good long apron that you leave in the shop. When doing really dusty things, also wear a smock, scarf and hat, then blow yourself off well and wash up before leaving your shop.
- Also provide good chip collection which used to be called dust collection. Although many make chip collection seem complicated it really is well understood. Since the 1920's firms have been required to provide good chip collection. Good chip collection keeps floors, tools and work surfaces clear of sawdust to minimize accidents and fire risk. Good chip collection requires about 350 cubic feet of air per minute (CFM) air volume at most small shop stationary tools. We need to move this air at a speed of not less than 3800 feet per minute (FPM) to pull in the sawdust and chip plus keep our vertical ducts from plugging. We also need to maintain at least 2800 FPM airspeed in our horizontal ducts to keep them from building up piles. Dust piles in ducts pose a serious fire hazard. When these piles break loose is just about the only time in small shop woodworking where we can get a potentially explosive dust to air mixture.
- A broom and dust pan will clean up the sawdust, but I prefer using my Jet 1.5 dust collector with its upgraded fine filter to control the sawdust when firing up the cyclone would be a chore.
The next step which involves collecting the fine dust is much harder. We already know that a good shop vacuum does an excellent job of collecting the fine dust for some of the new tools that totally enclose the working area. Unfortunately, such tools are expensive and most traditional tools cannot be made to totally trap the dust. Fortunately, those firms who guarantee customer air quality have shared exactly what we must do to get good fine dust collection at most traditional stationary tools like we use in our small shops.
- Experts found long ago that we make so much fine dust and it spreads so quickly that air cleaners and exhaust fans have zero chance of clearing the air fast enough to avoid failing an air quality test. This means the only way to get good air quality is to collect the fine dust as it gets made before it has a chance to spread.
- To get good source dust collection we must start by upgrading tool hoods to block and trap all the fast moving dust laden air streams. My ducting page shares many good hood solutions.
- The top experts who guarantee customer air quality found most small shop stationary tools need about 1000 CFM to get good fine dust collection. At first this might not make since. Why would we need three times more air volume to collect fine dust that we can move with the slightest breath? The reason is simple. Blown air hangs together a long time before becoming dispersed. Sucking pulls air from all directions at once so airspeed falls off at four times Pi times the distance squared. We need at least 50 FPM out to over 15.26" around the working area of our tools to pull in the fine dust before normal room air currents can disperse it. Building this big bubble requires moving lots air, far more than what we need to just pull in the heavier sawdust and chips.
- Unlike compressed air or air pulled by a vacuum cleaner, the low pressure air used for dust collection will barely compress at all. Any small hose, small tool port, or sharp bend in our ducting or hoses will kill our airflow just like partially closing a water valve. At typical dust collection blower pressures a 4" duct will only support about 350 CFM, a 5" only 545 CFM, a 6" only 785 CFM, and a 7" only 1069 CFM. This means at typical dust collector blower pressures we need at least 7” diameter flex hose and ducting to move the required 1000 CFM for good fine dust collection from most stationary tools. What I do for my cyclone designs is use an over sized blower which generates about 12” of pressure. This permits me to get a real 1000 CFM through a 6” duct but doing so makes more noise and wastes power.
- The experts show most tools need either a larger port or an extra port. Almost all current tools are setup to move about 350 CFM which only requires a 4" port to pass enough air to collect the heavier sawdust. To fix my band saw it required adding a 5” port under the blade and a 4” pickup port over the blade. Likewise, my table saw needs its cabinet port plus a 4" port on the blade guard the covers the blade and keeps that blade from spraying dust all over.
- Picking the right kind of blower is easy. Our blowers must overcome roughly 7" of resistance between our hoods, ducting, and filters. A typical squirrel cage blower does not work because they only generate about ½” of pressure which is too little pressure to overcome our resistance so we get almost no airflow. Shop vacuums generate over 60" of pressure but even the largest rarely move over 250 CFM which is too little air to pull in the fine dust before it escapes. Airfoil and caged blowers move enough air at enough pressure, but their impellers (fan blades) clog and cannot tolerate material hits from knots, chunks, hardware, etc., so we must use a material handling blower just like we see on almost every dust collector and cyclone separator.
- Our material handling blower must move at least 1000 CFM with at least 7” of pressure to overcome the resistance of our hoods, flex hoses, ducting, and filters. Blower technology is mature meaning blowers of the same types and speeds from different makers all perform near identically. Sadly, most of the less expensive import blowers found on small shop dust collectors and cyclones are not nearly as well made so tend to move much less air. The bottom line is no dust collector blower less than 3 hp or cyclone less than 5 hp will move enough air. The cyclone blower needs to be bigger to push the air to spin in a tight separation spiral inside the cyclone. Using smaller blowers may pickup the visible sawdust but will not do a good job on collecting the fine dust.
- They also found the best way to deal with the collected fine dust is to separate off the larger particles then simply blow the remaining fine dust outside. Fine dust will last forever if kept dry, but almost any moisture causes it to quickly breakdown. Use of infrared heat dishes deals with the heat loss from venting outside in even the coldest climates, but in hot areas and in areas where you cannot vent outside, you then need to air condition and filter. Likewise, many like me live in areas where it is illegal to vent outside, so we must filter.
- If you must filter then you should use a good cyclone separator that keeps the chips out of our filters because chips jam the filter pleats so when cleaning they poke holes and ruin our fine filters. Almost any cyclone will do this well, but expect to need to replace your fine filters roughly every three months of full time work. The problem is airborne dust ruins fine filters because it gets into the filter pores where the razor sharp edges and sharp often barbed points coupled with cleaning cause this dust to tear up the filter strands. This opens the filters and although they may still filter off the visible dust, they soon freely pass the unhealthiest fine invisible dust.
- Frustrated by the high cost of fine filters, need for constant cleaning, and short filter life I designed a much more efficient cyclone that separates the airborne dust six times better than any other option. This cyclone worked so well Clear Vue Cyclones licensed this design from me and now makes these units in a clear tough plastic, the same stuff used to make police shields. I personally am not allowed to vent outside, so vent my 1200 CFM cyclone into a pair of “200” square foot cartridge “nano” filters I bought from Wynn Environmental. I also made my own air cleaner using an 8” in line duct fan that produces nearly 800 CFM. That fan sits on weather stripping on a third “nano” filter. My gauges show it takes about 3 hours of that air cleaner running to pull the dust level down in my home to what is considered medically safe even on the smoggiest days.
If you want lots more detail and free plans to built the units I use to protect my family, please visit my Cyclone and Dust Collection Research pages. Still, the bottom line for most is even if it is work to get good fine dust collection, good fine dust protection is easy, always wear a good properly fit dual cartridge mask while making dust and use a good commercial duty fan that you run while working and for at least thirty minutes after your woodworking to avoid building fine dust. Enjoy.