Cyclone and Dust Collection Research

Welcome to the updated Cyclone and Dust Collection Research web pages.
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  1. Disclaimer


  2. Ducting Introduction

    This page translates the engineering ducting solutions that the experts who guarantee customer air quality use. If you have not already read at least the Home and Medical Risks pages, you should read those pages first to better understand fine dust risks and how poorly most do at providing good protection. The peer reviewed medical research is clear that every fine dust exposure causes a measurable loss of respiratory capacity, some of this loss becomes permanent, the larger and longer the exposure the greater the damage, and in spite of this damage from each exposure being small the damage builds over time to eventually cause asthma, COPD, emphysema and also worsens other age-related diseases often resulting in shortened life spans. The problems are many. Almost all small shop vacuums, dust collectors, cyclones and air cleaners miss collecting significant fine dust. Worse, most small shop vendors sell too open filters that freely pass the unhealthiest invisible fine dust and they also sell undersized filters which causes these filters to rapidly wear out and then freely pass the finest unhealthiest dust. OSHA testing shows that with every twenty pounds of sawdust we make enough fine dust to cause 15,119 typical two-car garage sized shops to fail an EPA air quality test. Fine dust lasts nearly forever unless it gets wet. Most vent our dust collection systems inside which allows the fugitive dust that escapes collection to build to dangerously high levels. Almost all hobbyists and six out of seven professional woodworkers work in small shops that are not government inspected or covered by any standards except what we choose to put in place for ourselves. Most home insurance inspectors, building inspectors and fire marshals will fail almost all small shop dust collection solutions due to serious safety concerns. Worse, government testing shows almost all even very clean looking small shops build up so much fine invisible dust that just walking around without any additional woodworking launches enough fine dust airborne to fail EPA air quality tests. The earlier pages on this site explain how to get good fine dust protection without having to install good fine dust collection. This page assumes you have already decided to move forward to good collection. Good collection requires ample airflow along with having the right hoods, tool ports, tool internal ducting, flex hoses, duct, wyes, blast gates and other components to support the level of dust collection we want. We need to follow the expert advice to ensure collecting the fine dust, transporting it for disposal, then getting rid of it.

  3. Basics
    1. Dust Volumes

      As shared previously fine invisible dust is so unhealthy that the EPA sets very tough indoor air quality standards. Woodworking makes huge amounts of fine dust compared to how little it takes to exceed these standards and harm our health. On average with every twenty pounds of sawdust we also make enough fine invisible dust particles to cause 15,119 typical two car garage sized shops to fail an EPA air quality test. So, unless we use tools that totally enclose the dust making activities, when woodworking we need to worry about fine dust. Where this dust comes from is simple. At a microscopic level wood consists of dry very brittle tubes, so every time we work wood with blades, bits, cutters and sandpaper these tiny tubes explode into millions of fine invisible airborne dust particles. Just about every woodworking machine and hand tool operation launches fine dust particles airborne. A particle counter shows making a perfect long shaving with a razor-sharp hand plane that makes no visible dust launches millions of fine invisible particles airborne. These fine particles get by our natural protections then lodge deep in our respiratory tissues where they do damage and release toxic chemicals.

    2. Existing Dust Collection

      Most existing small shop dust collection equipment works poorly because most small shop vendors do not follow industry standard practices to build dust collection systems. They provide undersized insufficient horsepower blowers, improperly sized ducting with poorly designed and made fittings, blast gates, and tool hoods. They also improperly locate our equipment, store sawdust to create a serious fire hazard, and generally use undersized far too open filters. This page addresses each of these problems. In addition to this equipment providing poor dust collection, almost all existing small shop dust collection equipment provides terrible fine dust collection. The makers of these tools don't understand the difference in the physics between sucking and blowing. We all know from using our shop vacuums on blow that blown air will hold together for many feet and blow stuff all over. We also know from using these same shop vacuums that the only way to pick up sawdust when sucking is to get our hose or attachment right next to what we want to suck up. The reason is sucked air comes from all directions at once, so airspeed falls off at roughly twelve times the distance squared. In simple words this means normal room air currents are moving faster than our sucked air so the fine dust gets blown all over. This helps explain why a system that can suck up a tape measure or heavy tool can't do a good job collecting the fine dust that we can move with the slightest breath. The problem is normal room air currents move faster than sucked air currents so will blow the fine dust all over.

    3. Dust Collection Standards

      Fortunately, the better air engineering firms that sell dust collection equipment and guarantee customer air quality share what they found must be done to capture the fine dust before it can escape. Since we use the same size and types of tools as smaller commercial tools, most of what we need to do for good fine dust collection is already laid out in detail. They set minimum standards that those who install their systems must follow to ensure good fine dust collection. Many publish their information on the Internet such as Cincinnati Fan Engineering Data. They provide simple formulas and approaches to help design our ducting to move the needed air with ample volume and speed at each tool. They also share the air speeds measured in feet per minute (FPM) we need to pick up various materials including sawdust and chips. They also give the airspeed needed to keep these items entrained meaning airborne in our ducts. They share that we need the right sized ducting to carry each different airflow. They also provide equations to help us properly size our ducting. Ducting size is very important as too small limits the total air volume and too large lets the airspeed drop so low that the dust builds into large ducting piles. Wood dust piles in our ducts can reduce airflows and cause plugging, but the more serious danger is piles of wood dust in our ducts pose a serious fire hazard as any spark that goes into a pile can quickly get fanned into a dangerous fire. The most common problem with duct piles is when they break loose they slam down the duct hard enough to blow apart our ducting joints and go right through separators then destroy blower impellers, bearings and filters. These experts share how to avoid these piles. They found we need the same airspeed to pick up the chips as we do to keep them moving in vertical ducting runs. They also found because we are not working against gravity in horizontal ducting runs we can get by with a little less airspeed to keep the dust moving. They found we must maintain airspeed inside our vertical ducts of 3800 FPM to collect most sawdust and up to 4500 FPM for larger chips. That means we also need these same air speeds to keep the vertical runs from plugging. We need at least 2800 FPM to keep the horizontal runs clear. Most air engineers add a little safety factor so design their systems to provide at least 4000 FPM airspeed in the vertical runs and 3000 FPM in horizontal runs. If you need to pick up larger chips and small blocks you will need to step up to the 4500 FPM airspeed.

      The experts also did considerable research which they have refined with decades of testing to work out how much air volume is needed at each size and type of tool to get good chip collection and get good fine dust collection. They found almost all small shop stationary tools get good collection of the same sawdust and chips we would otherwise sweep up with a broom with just 350 CFM of airflow. Fine dust particles are so small they are invisible without magnification. Fine dust particles are also so light they behave more like an odor so almost any air movement will blow the fine dust all over. They found to collect fine dust and overcome normal room air currents, we need to be pulling in the air at least 50 feet per minute out to a distance of just over fifteen inches all around the working areas of our tools. Clearly the larger the tool working area the greater the air volume required. Air speed and air volume are related with a simple formula FPM = CFM/Area where area is measured is square feet. With our knowing how far out we have to move this 50 FPM airspeed we can calculate the CFM meaning cubic feet per minute air volume. We end up calculating the surface area of a sphere with a radius of just over 15 inches, convert that to square feet then solve this formula and find most small shop tools need right at 1000 CFM airflow for good fine dust collection. This explains why it takes nearly three times more total air volume to get good fine dust collection that it does to pick up the same visible sawdust and chips we would otherwise sweep up with a broom. Clearly, to get good fine dust collection we have to move lots of air to pull in the fine dust before it gets blown all over. The experts did considerable experimenting and testing, followed by decades of refinement to establish the CFM requirements tables. This table from AAF shows what airflow measured in cubic feet per minute (CFM) we need to collect at each type and size of woodworking tool before it can escape.

      The experts also found these CFM tables are worthless unless we also modify our older tool designs. They found most older tool designs spray fine dust all over unless we upgrade the tool hoods, ports and internal ducting to protect, control, and deliver the fine dust for collection as it is made. They found it is impossible to get good fine dust collection on almost all older tools and many newer tools unless we either totally enclose the dust making activity, or upgrade our tools with better hoods that prevent the fine dust from spraying all over. This makes sense because most blades, bits, cutters and even sandpaper launch dust filled air streams at over 100 miles an hour. Dust collection systems rarely move air at much over 40 miles an hour. That race is always lost unless we upgrade our tool hoods to control and deliver the fast-moving dust filled air streams for collection. Also, with permission below shares some of the vendor recommended hood and collection designs for most major tools.

      Air engineers also came up with the formulas, charts and fan tables to ensure we have the right ducting and blower. They built static calculators like the one linked here that estimate the resistance created by our ducting, flex hose, duct fittings, hoods, filters, cyclones, separators, etc. They provide blower fan tables that let us use our airflow requirement and resistance level to look up what sized blower with the right size impeller and motor to move the amounts of air we need. They also formalized this process into something that most can follow without special training or expertise to come up with a good dust collection system. Each of us can go through this process to determine our needs, pick a blower large and strong enough, configure our ducting, separate off the heavier dust, and either exhaust the fine stuff outside or appropriately filter that dust.

    4. Resistance

      Because air will compress, I wrongly assumed the air would just speed up to give us nearly the same flow on both sides of a small obstruction. Based on that bad assumption, I used tapered adapters going right to my machines that connected to their built in 4" ports. I then received an email that asked me to further clarify, because in many instances this will not work. I pulled out my gauges and found out I was dead wrong. My further research and testing showed at the low pressures we use in dust collection, air is more like water, and barely compresses. (my thanks to Dave for reminding me that under typical dust collector pressures air is virtually incompressible). Any obstruction will kill our airflow dramatically just like closing a water valve. This means any obstruction, small pipe, small port, tight turn, undersized hood, restrictive internal air pathway in a tool, undersized hose, or restrictive duct fitting will act just like a water valve and seriously reduce flow. This also means our tapered and smaller adapters from our ducting to our tools are all but useless because they also kill our needed airflow.

      When we have high resistance from an obstruction or rough ducting that resistance will control the flow. To test this for yourself, try a simple experiment I learned in engineering classes long ago. Get a few feet of 1/8" interior diameter clear hose. Now cut off about a 1/2" of this hose. Without choking on that tiny piece, try to breathe through it. Most can but find it difficult. Now try to breathe through the longer piece. Most cannot because it has too much resistance. Now go back to the small piece and try to breathe through it quickly. You cannot because our lungs cannot create the pressure needed to overcome the high resistance of that small pipe. The same is true of our ducting. The resistance and size of the duct will define the airflow. One common mistake is to use standard flex hose as most of this hose is poorly made with ribs sticking into the airflow adding up to nine times the resistance of smooth pipe. Always buy and use a minimum of smooth interior walled flex hose as it that only adds about three times the resistance of smooth pipe. If we use too small of ports, duct, fittings, or outlets, or we use too rough of duct we kill the airflow needed for fine dust collection.

      Because air is near incompressible at the low pressures we use in dust collection, we end up with the pipe diameter and resistance controlling our air volume. This is just like water. We open and close a valve to regulate how much water comes out of our faucets. To support the minimum 1000 CFM we need for fine dust collection, we need to upgrade our 4" ducting and tool port connections to a total area the same as the opening area of a 7" duct or we must use a bigger more powerful blower that generates the pressure to pull ample air through a smaller duct. It costs so much more to use a bigger blower and motor that most only compensate one ducting size. So the airflow that normally requires a 7" duct can be carried in a 6" without too much trouble, but gets much more difficult and expensive without more powerful blowers. For instance, my table saw came with just a single 4" port on the saw cabinet. It seemed to work well enough until I got a particle counter. Then I realized that my table saw was a huge dust pump. I measured its airflow and even with my large 5 hp cyclone only about 350 CFM was moving through the ducting when collecting from that saw. To increase the airflow amply to get good fine dust collection I had to change the ducting to a larger down drop that split into two collection hoses. One 5" hose connected to the saw cabinet and I had to add a hood with a 4" duct. My air gauges showed that was still not working, so I discovered there was a 4" hose inside the cabinet that went to a lower blade guard connector that also had to be upgraded to 5".

    5. Ducting Diameter

      Air at dust collection pressures is little more compressible than water, so any small opening, small port or obstruction acts like a partially closed water valve and controls our flow. Remember that just one obstruction, our water valve will totally control water flow. Opening the faucet wide with the biggest possible pipe or hose gets the maximum flow. Clearly a garden hose would empty a city water tank far slower than a large pipe. Similarly, ducting size has everything to do with how much air you can move at a given pressure.

      This chart shows a 1.5 hp dust collector that can move a maximum of 1100 CFM moves far less air than that maximum depending upon what sized ducting we use. Typical small shop dust collector and cyclone blowers only generate about half of their maximum possible pressure when working, so run in the 4" to 6" of pressure range when working. With the added overhead of our filter and minimum ducting, that pressure is only ample to move about 785 CFM when hooked up with 6" diameter duct. That pressure will only pull about 550 CFM when connected with 5" duct and only about 350 CFM when hooked up with 4" duct. It is even less with flex hose because flex hose has so much more resistance.

      Air engineers design our dust collection systems to provide good collection for the least energy. Chip collection collects the same sawdust and chips we would otherwise sweep up with a broom. Chip collection has been a requirement in many areas since the 1920s so is well understood. Decades of experience show we need at least 3800 FPM air speed to provide initial chip and sawdust pick up and at least this same 3800 FPM air speed to keep our vertical runs from plugging. We also need at least 2800 FPM in the horizontal runs to avoid building piles that pose a serious fire danger and can ruin our dust collection systems and filters when they break loose. Most air engineers design a safety factor so target 4000 FPM air speed in our vertical ducts and 3000 FPM in our horizontal. Additionally, air engineers have studied almost every brand and size of tool to determine how much airflow is needed to provide good chip collection. Almost all small shop stationary tools require 350 CFM airflow or less to get good chip collection. Once we know the air speed and air volume we can then use the air formula FPM = CFM / Area where Area is in square feet to calculate our ideal size for ducting. With 4000 FPM needed to collect and transport the dust in vertical runs and a 350 CFM air volume the math shows 4" diameter duct gives a real 349 CFM which is near ideal for pick up and keeping vertical runs clear. Using the next larger duct, meaning 5" shows we don't get enough air speed to keep our vertical runs clear, so our ideal chip collection system will all use 4" diameter duct.

      We can move fine dust particles with the lightest breath, so decades of experience show most stationary small shop tools require at least 1000 CFM airflow to capture the fine dust before it gets blown all over by normal room air currents. This 1000 CFM requirement poses many challenges. Blower technology is mature meaning if you buy the same type, size and speed blower from any of the major blower makers you will get near identical performance. Sadly, most small shop vendors sell blowers that do not perform nearly as well, so the commercial blower tables often show much better than what we can buy from our small shop vendors. These blower tables show at typical dust collection pressures we need at least a 3 hp small shop dust collector or 5 hp cyclone to move our 1000 CFM required for good fine dust collection. Using the air formula with this 1000 CFM and our 4000 FPM requirement it shows we need all 7" diameter ducts and down drops. The fan tables show 7" diameter ducting is so large that all commercial dust collectors and cyclones generate too little pressure to maintain the airspeed needed to keep our vertical runs from plugging. With the small shop blowers all being equal or less in performance, this creates a problem. Stepping down to 6" diameter ducts gives us plenty of air speed to keep the vertical runs from plugging but drops the air volume to our tools to only 785 CFM which is too low to get good fine dust collection. Bottom line, if you have today's normal dust collector and cyclone blowers, you are limited to either living with 785 CFM airflow with 6" diameter ducting or you can get your 1000 CFM with the 7" diameter ducting but will have some plugging in vertical runs.

      There were no small shop dust collectors or cyclones that resolve these issues, so I came up with my own solution. I used an oversized blower with larger impeller and larger motor that generated enough extra pressure to meet both the airflow and airspeed requirements. This makes for more noise but results in great fine dust collection, so now all of my cyclones and those sold by Clear Vue use these oversized blower wheels and higher horsepower motors that move a real 1200 CFM through 6" diameter duct with plenty of extra air speed for good pick up and to keep the vertical runs clear. Additionally, since the more air a blower pushes the higher the amp draw my designs also use restrictions to ensure our blowers can't move so much air that we burn up our motors. During the magazine testing I oversaw three different vendors had cyclones burn up because they did not amply limit airflow. Always check your motor with an amp meter to ensure your maximum airflows do not pull more amps than your motor can support. Most knowledgeable woodworkers who build their own systems use oversized blowers ample to support 6" ducts and 6" flex for down drops and either 7" or 8" ducts for horizontal mains..

    6. Leaks


    7. Airflow Requirements


    8. Power requirements


  4. Layout & Ducting Design





    1. Fire Safety


    2. Pipe Size

      Always use the largest diameter duct that your blower can support with the least number of restrictions. If your ducting is too small, then it instead of your blower defines the CFM that your system can provide at your machines to pick up the dust. If your ducting is too large you might not maintain the airspeed needed to keep sawdust and chips from building up and blocking your ducting. Air engineers design dust collection systems to have 3000 feet per minute (FPM) airspeed to keep all entrained (moving) horizontally and about 4000 FPM to move it vertically. As discussed before we need at least 3 hp small shop dust collectors or 5 hp cyclones and then can only use 6" diameter duct for verticl runs which unless we use oversized blowers will only move 785 CFM. That 785 CFM is too little for the 1000 CFM required for good fine dust collection. Likewise, we have to do some careful measurements to pick our horizontal duct as we need to keep the size large enough to carry our needed air volume without getting so large that the air speed falls below 3000 FPM or we get piles that pose a fire danger and can ruin our equipment when they break loose. For almost all small shop systems this works out to using the same sized duct for the mains as the down drops. With the oversized blowers used in my designs you can safely move up to 8" diameter mains. I passed on the 8" or 7" mains when I found the fittings too expensive, so in my shop I use all 6" diameter duct for mains and downdrops. It consistently provides over 1200 CFM at all my tools with plenty of airspeed to keep all clear.

    3. Ducting Resistance

      Ducting resistance is known as static pressure. Even a short run of duct that is too small for a blower will cut the airflow down to the highest speed that pipe can sustain. The impact on most hobbyist blowers is terrible. A 3/4 HP blower with a maximum airflow of about 600 CFM will rarely provide more than about 300 CFM real air flow when connected to a 4" pipe. On that same 4" ducting a 1 HP and larger units still only move about 350 CFM. A 2 HP dust collector capable of 1200 CFM is lucky to provide 450 CFM. Bumping up to 5" pipe supports 545 CFM. Bumping up to 6" pipe supports 785 CFM, but anything less than a 3 hp blower then lets the pressure and air speed fall enough that we get plugging in vertical runs. Clearly we need 4" diameter duct for good chip collection and at least 6" diameter duct with oversized blowers for good fine dust colleciton.

    4. Ducting Reductions

      Unlike big industrial sites, most hobbyists should run the same sized ducting, fittings and hose right up to their machines. Don't do like many and run a 6" or 8" main trunk line then come off with smaller duct or flex hose. The top magazine rated cyclone vendor designed and supplied the ducting for their cyclone I installed in my shop. They had as small as 1" diameter down drops which measured with only 22 CFM airflow letting all collect in the mains. When I opened larger ducts the piles in the mains slammed down the ducting so hard they blew apart my joints, ruined my blower wheel, and destroyed multiple filters in less than six weeks use. Smaller pipe kills the airflow needed to keep the air in the mains moving fast enough to avoid plugging and building up dust piles. You have to keep three 3" ports open at once or two 4" ports to avoid the plugging a 6" main and even more open for larger mains. Having so much open often kills the airflow needed to collect the fine dust. If you use standard hoods you should still convert over to 6" ports. Even reducing ducting size right at the machine for the shortest possible distance to a small 4" port will still kill system performance. The smaller ducting, flex hose, and small ports limit the maximum airflow just like we proved in that little air test sucking experiment! If you do change size ducting, use a big enough blower to support opening multiple blast gates and appropriate connections for enlarging and reducing:


    5. Ducting Material

      The next most important aspect of building a good ducting system is which type of ducting material you will use and still ensure the level of safety in your shop. If your shop is going to be subject to a building inspection, fire marshal inspection or insurance inspection, then you need to use all steel ducting. Almost all small shop dust collectors and cyclones are gravely underpowered, so we need to use the smoothest pipe we can get to minimize resistance that rapidly kills these lower airflows. To minimize resistance, the interior of the pipe needs to be as smooth as possible and you need long smooth sweeping smooth bends on all your elbows and wyes. Also, air needs to spill over the joints, not ram into them which causes high resistance and causes strings and such to get stuck in the duct joints. There are lots of ducting choices and often we slip into a mode where we think if something costs less it is not as good. The smoothest walls that make for the least resistance come with using plastic coated pipe and fittings such as PVC pipe or plastic coated metal or wood duct. The next best is smooth walled laser welded steel pipe followed by top quality metal spiral dust collection ducting and fittings then HVAC metal duct, followed at a far distance by corrugated metal pipe and flex hose. Airflow depends upon ducting friction. Here are the Hazen/Williams friction factors for various duct types (a higher C number is better).

      Duct Material H/W
      Corrugated Steel Duct 60
      Spiral Duct 90-100
      Laser Welded Steel Duct 110-125
      PVC 146


      Unfortunately, many wrongly think that they can easily use HVAC ducting for their dust collection systems. HVAC air blows in the opposite direction as it does during dust collection, so every joint is backward. The good news is all but HVAC wyes can be turned around to get the air moving the right way. We can either use expensive dust collection wyes or do the metal working to change the male and female ends.

      We need to be careful when buying either dust collection ducting or HVAC metal pipe. We can easily spend a small fortune and still not end up with a system that works efficiently or is leak free. Also, most "official" dust collection pipe uses proprietary connectors and sizes that often limit your expansion to working with just that firm. With special tools required to make junctions, you also end up generally paying for a number of custom made parts. I started off using HVAC snap lock duct and quickly learned I don't like fighting with snap lock and I had to use the heavier 26-gauge because just like with one of the cyclones I built, standard 30-gauge collapses if the system gets turned on with no blast gates open. There were other problems with HVAC ducting. The HVAC wyes need the male and female ends reversed. I had so much ducting the cost to buy actual dust collection wyes with the correct ends was too high, so I invested around $100 buying on sale an inexpensive Harbor Freight knockoff of a Pexto machine that let me crimp the female joints into male then flatten and expand the male joints into female. Also, HVAC systems use such much higher volumes and lower pressures that are not as affected by tight turns, but the tight turning HVAC elbows add too much resistance for use with dust collection ducting. Purchasing long radius dust collection elbows was also cost probhibitive so I instead used two or three swivel HVAC ducts or used two 45 degree ducts with a straight in between to reduce resistance. With my constantly adding and changing tools as well as my shop layout, I rapidly grew to hate the HVAC snap lock pipe, so shifted to use spiral pipe which actually cost less and was easier to work. My new home with its own shop in a large separate building and elevated floor inspired me to foolishly place the ducting under the floor. After living under the crawl space with every change, I said never again, plus there were condensation problems that ended up rapidly rusting and corroding my duct. Another move left all my ducting for the new home owenr and put my shop back in a bay of my garage with my doing all over again. I was back to a garage based shop, so had to start all over again. I considered building square or rectangular ducts from Melamine coated particleboard because that material is inexpensive and very slippery so would have little resistance. After making a test run I gave up as that was too much work. One of my friends showed me an article that debunked the static explosion problems with PVC, so I used the thinner PVC pipe that is readily available and inexpensive in my area due to all the agricultural irrigation (see my PVC site if you want to do "magic" with fitting PVC into your ducting). The low cost sewer and Drain (S&D)PVC (plastic) pipe worked so well I used to recommend the PVC ASTM 2729 "Sewer and Drain (S&D)" pipe for most small shop woodworkers. The 2729 PVC pipe and fittings cost far less than metal or standard schedule 40 PVC, are much stronger, don't leak like metal pipe, and have a much lower coefficient of friction than even spiral metal ductwork. The 2729 PVC is rated for many times the pressure that even large industrial blowers generate. I've seen no flex with my PVC pipe even when doing testing on 10 hp blowers driving a 16" impeller. PVC then was one of the best small shop dust collection material choices because it is smooth, far stronger than most HVAC metal pipe or spiral pipe, costs less, and fittings are a fraction of the price. We then had a flood in our home from a burst water pipe. My insurance inspector said I could either replace the PVC duct and cardboard dust bin with metal or lose my tool and any fire coverage from a garage based fire. My State inspector also said any flammable ducting materials are totally inappropriate and will not pass either a building, fire marshal or insurance inspection. Health problems required me to retire my shop so I gave away my cyclone and PVC ducting. After a far too long break my health has improved enough that I can resume some limited woodworking. In the interim the price of oil has gone up so much PVC pipe costs more than HVAC pipe or even good spiral pipe. With limited ability and patience to play with ducting I am now using higher end steel sprial ducting that mates with cam action sealing laser welded steel duct fittings. They are very expensive and far beyond what I could afford when I first started doing woodworking.

    6. Ducting Cost


    7. Ducting Connections

      Making your dust collection connections can be done with glue, screws, special duct sealant, and many other things, but most find that slipping all together works best. This is especially true if you buy duct with the built in seals. They cost more but make tight joints that normally don't need anything more to hold them in place with a good seal. Most agree that not gluing PVC is by far the preferred way to go, as you may change your mind on your shop arrangement, and you will for sure eventually catch something that clogs requiring you to take one or more joints apart. I found on both the metal and PVC pipe, use of standard 2" aluminum duct tape found in home and HVAC stores provides great seals that do not leak or come apart. Be careful when handling this aluminum tape as it is very sharp! Permanent joints are better sealed with either duct sealing compound or polyurethane caulk.


    8. Duct Hanging

      There are lots of ways to mount your ducting to the ceiling or wall. After years of changes my technique now uses heavy wide long nylon cable ties and screw in mounting brackets.

      1. Wire

        The traditional approach for hanging duct some distance from the ceiling is to attach galvanized wire to the ceiling or to a metal pipe then around our ducting. This works well, but is difficult to adjust without a lot of practice or use of expensive turnbuckles.

      2. Metal Strapping

        The longest lasting and least expensive to install hanging system uses perforated rolls of galvanized sheet metal plumbers strapping. To mount flush with the ceiling you can make a U and secure both ends with screws. To hang you can mount to the ceiling, use a tape measure to get a consistent distance and equal length loop and then bolt that tape around your duct.

      3. Nylon Cable Ties

        Amazon carries wide heavy duty nylon cable ties that work well to secure ducting right to the ceiling, but these don't work well if your ducting hangs well below the ceiling. Although the nylon ties will eventually get weak and fail, most change their ducting and tools far more often than the years it takes for the ties to get brittle and fail. Here are pictures of ties and matching mounts that you can order from Amazon. If you use these links a small commission comes back to help support these pages. If this is a concern, you should use the galvanized perforated metal plumber's strapping.

        The easiest way to install the nylon cable ties is to use screw in mounts designed to work with these ties. The nylon cable ties are what gets used in my shop with its 8' high sheet rock covered ceilings to hold galvanized spiral duct. To minimize dust going into the down drops my mains are a 2x4 spacer below the ceiling with all down drops first going up to flush mount on the ceiling then dropping down to the tools. The sprial duct has one end crimped to form a male end which always go placed closest to the dust collection system. You can either use two forty-five degree ducts with a straight spacer, two swivel ducts or dust collection long radius elbows. My preference is the higher cost long radius elbows from a ducting store. Likewise, you either need to buy your wyes at a ducting store or use a roller and crimper to reverse the male and female ends. Layout your ducting design then follow that design using chalk lines on the ceiling to show the layout. Then use 2" sheet rock screws to secure the heavy nylon cable tie mounting brackets into the supporting studs. Thread the wide long nylon cable ties into the mounting brackets without connecting the ends except on the starting tie. The starting tie gets a large loop to hold one end of the duct. Slip the duct into the loop and use an adjustable stand to hold up the other end of the duct with spacer in place when needed. Secure the tie in the other end to loosely hold the duct up. Connect the rest of the ties loosely. Slip the male ducting end into the prior duct segment then use heavy aluminum tape to secure the joint. After all ducting is up with the connections sealed, I then cinch up the cable ties to pull the ducting to my ceiling or spacer. As a tool nut my ties get secured with a nice pistol type nylon tie gun that cinches up the ties and clips off the ends all nice and even. It can work too well and tighten the ties so much it is near impossible to remove the spacers, so just tighten to snug, not tight.

      4. Band Clamps


      5. Wire Rope

        Another solution for hanging duct is to use stranded metal cable (called wire rope) with special clamps that let you adjust the length. A number of firms make and sell different types of cable connectors. The simplest and most difficult to use are the "8" shaped metal ferrules that you squeeze onto the cable with a crimping tool known as a swager. I've been making massage tables using this kind of system since the early seventies and own three different types of swaging tools. Even with a lot of practice I either make all on a template or end up having to redo too many. Most boat supply stores sell both the cable and ferrules, or you can get them from a cable supply store. I bought on-line a large spool and a pound of ferrules for what it would have cost me to buy just a few pieces from a boat store. I've only helped do one shop with very high ceilings and this stranded cable. Using the compression ferrules was such a pain to get just right if I had to do it again I would pay for the adjustable fittings.

      6. Suspension System


    9. Pipe Under Floor


      1. Subfloor


      2. Concrete Slab







      3. Computer Floor


  5. Ducting Components
    1. Ducting Accessories







    2. Blast Gates










    3. Flex Hose & Hose Clamps



    4. Fittings


      1. Wyes



      2. Elbows


      3. Homemade Fittings



    5. Transitions












  6. Tool Ducting


    1. Dust Ports

      Most small shop users will have to upgrade their tool dust ports themselves and use the wrong types of ports. Sucked air comes from all directions at once, so if we use just a pipe going into our tool, what happens is the air coming from the sides or backside of the pipe picks up speed then rams into the air coming in from the front. This creates lots of turbulence, resistance and significantly reduces airflow. So although many use flat HVAC connections it is far better to use actual dust collection ports that have a really nice curved inlet. A bell shaped (hyperbolic) curve eliminates most of the problems from the air coming from the sides and back to reduce resistance and increase flow. I like the Lindab and Nordfab smooth walled laser welded steel take off flanges plus they and have a built in gasket. Also, these are very good looking smooth strong ports. Note it does not take much curve at all to make a huge difference.

      Most small shop users also mess up their ports. Most stationary tools need more than one port or hood instead of just a bigger port. For instance my table saw came with a single 4" diameter port. The stock blade guard sprayed fine dust all over, so after doing my homework I upgraded to a Lee Styron Shark Guard Whale sized over blade guard with a 4" port. That left me with a 4" port for my blade guard and a 4" port on my saw cabinet. I needed to figure out how much if any to increase the size on my cabinet port. The total combined area of the ports should closely match or just slightly exceed the area of our ducting. Rather than have to guess, I built the following chart that gives the combined areas for different sizes. We use this chart to pick two different diameters that equal or slightly exceed the area of the incoming ducting. The green shaded blocks are what most who use standard 7" diameter duct should use. The blue shaded blocks are what I use for splitting 6" duct. For example, let's connect my cyclone to my table saw with a 6" downdrop. This table shows my 6" diameter ducting has a cross sectional area of 28.27 square inches. I look at the table and see a 4" blade guard port with a 4.5" diameter port is the closest solution for my saw cabinet. I cannot affordably get 4.5" diameter duct or ports, so next best was a 5" diameter port which is the size added to my saw. So my saw got upgraded with a 5" cabinet port.


    2. Dust Hoods














      AAF Hood Design suggestions

      Other professional hood designs:

      Saw Blade Guard

      Floor Sweep Setup Floor Sweep

      Random Orbital Sanders NIOSH Recommendation



      Shaper NIOSH Recommendation



  7. Static Electricity


    Explosion or not, getting a good zap while next to a sharp blade or cutter can be plenty dangerous, so if you live in a dry climate and chose to use PVC, you might want to seriously consider protecting yourself. We cannot ground PVC because it is an insulator, so all we can do is provide a way to bleed of static before it builds to unhealthy levels. Most do something which works poorly which is to run a single grounded wire around the outside of your PVC. If done right that wire also attaches to the metal coil spring inside your flex hose then you ground that wire both at your machine and your blower. However in dry climates, static can be a real pain around tools and doing a better job of grounding your dust collection piping is worth doing. As I said before most grounding approaches do not work well at all and most attempts to put metal inside our ducts leads to plugged pipes. Here is a workable solution shared by one of the many contributors to this site. Thanks for sharing Brent!






  8. Noise Control












  9. PVC Confusion






  10. Frequently Asked Ducting Questions








      SPIRAmir Corp.
      6780 Sierra Court, Unit "M"
      Dublin, CA 94568
      Phone: (925) 803-8444
      Fax : (925) 803-8448
      Air-Duct Mfg., Inc.
      920 N. Lombard Road
      Lombard, IL 60148
      Phone: (630) 620-9866
      Fax: (630) 620-9878
      Die Stamped Products, Inc.
      1230 S. Manufacturers Row
      Trenton, TN 38382
      Phone: (731)855-0040
      Fax: (731)855-0460












































  11. Disclaimer





Copyright 2000-2020, by William F. Pentz. All rights reserved.