Bill Pentz and Cyclone Test

[Walt Nicholson]

I have never been the sharpest knife in the drawer but has any group or organization done a definitive study of the long term effects of sawdust on woodworkers nationwide? Years ago studies were done about the number of people who died of "black lung" disease from coal mines, and the number of deaths and problems from asbestos and paint in automobile paint booths, but I have never seen anything about woodworkers. I know some people who could probably eat poison ivy for lunch and never be bothered and others who go into hiding when the pollen is around in the spring, so it is natural to expect some people to have allergic reactions to some (or all) types of sawdust. Here in the northwest we have had many, many mills in operation for years with more sawdust in the air than you can imagine but no epidemic or widespread indications of lung disease or sawdust related deaths. I also know that you can violate OSHA standards if you paint a railing the wrong shade of yellow. I can remember my grandmother using a broom to dust the sawdust off of us kids after we had been watching grandpa work in his wood shop. He died of old age at 89. My dad followed in his footsteps and died of old age at 91. I feel worse physically sitting at a stoplight and breathing the diesel fumes from the truck in front of me than standing in my shop smellling the sweet smell of fresh cut wood. I may be too old and stubborn (and dumb) but I will die happy, covered in sawdust, before I will subject myself to working in a sterile, "clean room" environment with hoods and respirators and such like some nuclear facility as some people in these posts advocate. I have a Delta ceiling mount filter and a good DC setup and call that good for me. Now I will quit my rant and go make some more sawdust. Just an opinionated old fart.

[Bill Jepson]

I have never been the sharpest knife in the drawer but has any group or organization done a definitive study of the long term effects of sawdust on woodworkers nationwide? Years ago studies were done about the number of people who died of "black lung" disease from coal mines, and the number of deaths and problems from asbestos and paint in automobile paint booths, but I have never seen anything about woodworkers. I know some people who could probably eat poison ivy for lunch and never be bothered and others who go into hiding when the pollen is around in the spring, so it is natural to expect some people to have allergic reactions to some (or all) types of sawdust. Here in the northwest we have had many, many mills in operation for years with more sawdust in the air than you can imagine but no epidemic or widespread indications of lung disease or sawdust related deaths. I also know that you can violate OSHA standards if you paint a railing the wrong shade of yellow. I can remember my grandmother using a broom to dust the sawdust off of us kids after we had been watching grandpa work in his wood shop. He died of old age at 89. My dad followed in his footsteps and died of old age at 91. I feel worse physically sitting at a stoplight and breathing the diesel fumes from the truck in front of me than standing in my shop smellling the sweet smell of fresh cut wood. I may be too old and stubborn (and dumb) but I will die happy, covered in sawdust, before I will subject myself to working in a sterile, "clean room" environment with hoods and respirators and such like some nuclear facility as some people in these posts advocate. I have a Delta ceiling mount filter and a good DC setup and call that good for me. Now I will quit my rant and go make some more sawdust. Just an opinionated old fart.

Walt,
There have been a number of studies about people working in lumber mills getting "brown lung." ANYONE who works continuously in a high particulate atmosphere will have problems unless they protect themselves, period. This seems sort of obvious now. People will react at various levels. Some will simply be mildly irritated, and others will need to avoid the activity altogether. Everybody has heard of some elderly person that has smoked since they were 15 and they lived to 93. But then a BUNCH died of lung cancer at 54 too. The problem is that we should inform people, without rancor. If you chose to use a resperator great. If you don't it is YOUR choice. The problem is that many sensitivities build up over time. When you see the first problem you are already done and there is no going back. You then face a risk every time you do the projects that you enjoy. Currently no one would argue that hearing loss is cumulative, they simply KNOW that it is. If you work continously in a 100 decibel environment without hearing protection you WILL go deaf. Heck check out all the old rockstars sporting hearing aids! If you do occasional WW you probably won't have the level of problem Bill Pentz had. On the other hand, you might. I'm no nervous ninny, I used to race motorcycles so I can't be overly safety concious! But telling people what MIGHT happen and letting them decide if they want to take action is a flat out GOOD IDEA. Showing them how to minimise their risks is an EVEN BETTER IDEA! Thanks Bill Pentz for being the torch-bearer on this one.
Bill Jepson

[Walt Nicholson]

I appreciate your input and you have some very good points. I agree that it is good that we are informed of the dangers that face us in the shop although there seems to be varied opinions in this forum as to the amount of the danger and to the credentials of the people defining the danger. That is why I asked if there were any definitive (clinical) national studies done that document deaths and illness related to woodworking/sawdust. I had not heard of the Brown Lung disease that you mentioned and would like to learn more. When I googled it I got "Byssinosis (brown lung disease) a chronic condition involving obstruction of the small airways, severely impairing lung function. It is caused by dust from hemp, flax, and cotton processing. Between 1979 and 2002 byssinosis caused approximately 140 deaths." I will continue to look further for the association with sawdust as I do want to learn. I do not argue the obvious point that inhalation of any foreign substance into the lungs can be harmful and the people that are trying to prevent or reduce that inhalation are to be applauded. I guess I was just looking for case studies in lieu of opinions that would document the severity of the risk so that I could make a more informed decision as to the trade-offs between all out security and the enjoyment of the hobby. I certainly meant no disrespect to any member of the forum and their opinions.

[Rick Moyer]

... But telling people what MIGHT happen and letting them decide if they want to take action is a flat out GOOD IDEA. Showing them how to minimise their risks is an EVEN BETTER IDEA! Thanks Bill Pentz for being the torch-bearer on this one.
Bill Jepson

Well said Bill. I think this is what we really need to be thinking about when we read what Bill Pentz has to say. Many folks may think Mr. Pentz is "preaching" to them and get defensive. (maybe he is!??). We are each free to decide what is best for us, but we cannot make good decisions without some knowledge base for making those decisions. Everyone can chose to do or not to do what someone else might recommend,; but isn't it better to make your decision having a wealth of knowledge that someone has provided you? Kudos to Bill Pentz for providing it so I can make an informed decision for myself.

[Bill Pentz]

Your webpage update clears up some confusion…

Tim, I appreciate your questions but found that getting into the kind of detail you are asking for on a forum ends up in overwhelming amounts of detail that few hold of any interest, plus buries me in far more typing than I want to do. If you want to call or have me call you I would be happy to go over some of the detail that led me to creating a 1D1.64D cyclone design. In very lay simple terms my target was not just fitting my cyclone design under an 8’ ceiling but instead providing minimum airflow resistance and maximum fine dust separation. If you go to the ESSCO spreadsheet you mentioned, plug in a 4000 FPM airspeed which the minimum to pick up most sawdust and smaller chips and an 800 CFM air volume which is just about the minimum to get good fine dust collection at our stationary tools, that optimizer will spit out a cyclone that is about 13.5” in diameter powered by a whopping 7.5 hp motor. We can trade fine dust separation efficiency by expanding the sized of the cyclone diameter (D). The Cotton Research shows making D three times the main that feeds the cyclone is near ideal. So a 6” duct would make an 18” cyclone. Those with 7”, 8” and 10” cyclone inlets should be making 21”, 24” and 30” diameter cyclones. These will not fit under a standard 8” ceiling so they instead make smaller cyclones and increase impeller diameter and motor sizes. Anyhow, this all gets so messy that it is hard to cover in brief posts.

I noticed from your photo that you have a beard. Well, so do I. I use a similar mask for high risk operations like spraying, sanding and cutting MDF. I was wondering just how much dust makes its way around the mask through the beard.

Art, Yes I have a beard and it does cause some leakage but probably not as much as most as my hair is very fine and most has already fallen through going from the top of my head and out my nose, hands, ears, etc. Seriously, I pull my mask extra tight whenever making just a little fine dust or doing a little painting or spraying. It still leaks more than I want, so when making more than a little fine dust I end up wearing either my 3M or Racal Powered Air Purifying Respirator (PAPR). Both are near identical except my 3M also came with a second flip down welding mask visor option. Given Racal stopped making their units and the 3M are pretty pricey, for most I recommend that 3M 7500 unpowered respirator mask unless they are turners, have a heavy beard, or developing some sensitivities. My turner friends like the Trend Airshield powered respirators that work great with beards becase the air just gets blown out through any leaks instead of us sucking stuff in. That new Trend Airshield Pro is a near exact copy of my far more expensive 3M and I would like to hear when people begin buying these how well they work. Also, becareful what you buy has easy to find and affordable filters. I have a new off brand mask whose maker went under and you can no longer get its unique fitlers. Now if Phil would just share with us hairy guys where to get those HEPA beard filters…

I have a small shop in a tucked under (currently unheated) garage. It is hovering around 10 degrees outside now in MN and venting outside or leaving the garage door open doesn't seem like a good option.

Has anyone rigged up a dust collector with an air to air heat exchanger so that they can vent outside and capture most of the heat loss? If so, are there any ways to do it on a budget and is it that much better of an option than venting inside? ...

We move about the right volume, but our airspeeds tend to be pretty high so need a big unit. I asked one of my friends in the HVAC business and he ran some calculations and said most of the larger home heat exchangers would work well, or we could build one ourselves without too much pain. I don't know of anyone who has made one, so don't know how well they would work.

Bill J, Will, Walt & Rick, Thanks for your positive comments.

Walt,

Dust collection studies are a mess. There is really big money involved, plus a huge liability issue. There were peer reviewed medical studies in the fifties that linked long term dust exposure to a variety of problems. Since then we have far more information. These studies are pretty clear about the invisible without magnification 10-micron and smaller particles. A 10-micon particle is about one tenth the thickness of Art’s coarse beard hairs. The chemicals in and associated with wood cause specific problems for the particles all the way down. Those particles sized about all 2.5-microns and smaller have the added issue of causing serious long term major problems just from their size and shape. These are so well studied they now have their own shorthand name PM short for particulate material. Do a Google search on "PM 2.5 Health Risks” and you will see a load of credible studies that point out just the concerns from general particles of this size. I’d start my reading with the EPA discussion that defines what these are, explains the sizing and some of the other basics. Also, spend a little time looking over my Wood Toxicity Table to see some of the dangers from the chemicals from wood particles.

bill

[Abe Low]

I have been aware of the dangers of fine particles for several years before I met Bill. Bill has done wonders to spread the word in a way that makes the data believable. Everyone has the right to stick their head in the sand or believe that "I will be fine until it is my time". But it is a good thing to have the knowledge made available. If one is going to deny the evidence they ought to at least see the evidence.
Thank you Bill for being my Hero.
Btw, I met Bill for the first time when he was teaching at Sacramento State University in the Computer Science Department. He helped me greatly in preparing me to teach in that same capacity. If I recall correctly, he also taught at the University of California at Davis. At the time I didn't know he shared my love for woodworking. That part of our friendship came much later. Although it doesn't show through in his postings and his web site, he really is a very unpretentious fellow, that in addition to be generous, knowledgeable, and dedicated. Too bad he aint rich and good looking.

[Bill Jepson]

Bill J, Will, Walt & Rick, Thanks for your positive comments.

Walt,

Dust collection studies are a mess. There is really big money involved, plus a huge liability issue. There were peer reviewed medical studies in the fifties that linked long term dust exposure to a variety of problems. Since then we have far more information. These studies are pretty clear about the invisible without magnification 10-micron and smaller particles. <snip>. Also, spend a little time looking over my Wood Toxicity Table to see some of the dangers from the chemicals from wood particles.

bill[/color]

Bill,
It might help to actually define the size of the particles we are talking about here so people can understand what is involved. I work in the scientific Ultra-High-Vacuum industry making parts for the semiconductor industry, so I understand how small a micron is. For people working in other industries, and the non technical among us, (please note I did not say uninteligent), a micron is 1 millionth of a meter. In inches it works out to a bit under 1/25,000th of an inch. Or Real *&^% Little to use the vernacular. This is NOT regular "sawdust". Visible particles are usually removed by even a moderately good filter. Several of the guys have commented that they have no desire to work in a "clean room". That is perfectly OK. What you need to know is what the guys that put clean rooms together have learned about small particle research. When a particle gets this small it is so light that gravity can be a weak force compared to the smallest air current. Think of sitting by a window in strong sunlight. Ever seen the airborne dust floating around? Ever wondered what kept the dust in the air? The thing to understand is the harmful particles are even smaller than the ones you see dancing in the sunlight. Those are likely to be 10 microns or larger. When someone measures these particles they are in the air floating around even if you haven't been in the shop for some time. Getting the concentration of the particles low enough to be safe is what we are talking about here.
I don't want to lecture any body about this stuff either so I'll sign off now I hope that this thread has been useful to the general woodworking population of SMC.
Bill Jepson

[Rick Potter]

I have to admit my head spins when reading all the technical information here and in your website, but I keep at it trying to come up with a system I can afford that will pick up better than I have had in the past. I have corresponded with you in the past, and want to remind you of the burrito I owe you, and regret not having the opportunity to meet you when you went to San Diego. You went right past my place. Darn it!!

I sure hope you are planning to write a book about all your testing and research. If so, put me down for a signed first edition. It would be a great help to a lot of us to see all the research, charts, etc., along with pictures and floor plans of shops you visit, with real world information on how efficient various setup were in actual use. Most real testing we see in magazines shows a DC set up with a hose to a single machine. Pretty useless in real world terms.

Show us lots of pictures, floor plans, pipe layouts and sizes. Have a section on various popular brands of machines and the best hood types and sizes to use.

I realize this is a lot to ask of one person to include in one book, but you are the obvious person to write it; respected, great credentials, good with words, and with more personal research than anyone I know of.

Others have written books on this, but they have always seemed incomplete. This is your chance to write THE definitive book on dust collectors for the layman. After all, you are... THE DUSTBUSTER.

Glad you are feeling better.

Rick Potter

[Tim Marks]

I appreciate your questions but found that getting into the kind of detail you are asking for on a forum ends up in overwhelming amounts of detail that few hold of any interest.

Sorry, just the engineer in me getting out of hand. Obviously once you scratch the surface, what at first seems pretty simple quickly starts getting incredibly complex. I guess we should be thankful that there are big bucks in agricultural to keep pushing research on cyclones, because obviously little is happening from the woodworking side of the house to promote ongoing research. Thanks for opening the door a little bit on some of the other factors that have to be considered.

There is an increased popularity in vacuum-sized cyclones for use in the shop (with oneida's dust deputy kicking off this product line)? I have seen a number of people posting about the miniature cyclones that they have made using your spreadsheet to proportionately reduce the size. If someone was building this, would you recommend that they use a multiplier of 3 instead of 1.64 to define cone height (since they don't need to worry about ceiling space)? Of course, the resulting product might be a little top heavy...

[Dexter Hahn]

Hi, I'm new here, lurked for a while and as long as this good topic of dust collection is going, thought I'd jump in and ask for some advice. I don’t do that much WW, but I understand I need good dust collection, and I really don't want to invest the time and space to set up a complete cyclone and duct system, so I was thinking something smaller and moveable.
Bill what is your opinion on something like the Oneida portable?
http://www.oneida-air.com/newsite/portable.php
It has two smaller cyclones that they claim will separate out even sanding dust and a HEPA Filter opt. It looks perfect for what I need and looks better to me than some of the smaller machines with bags on them, I would just like a more experienced opinion. Thanks in advance.

Dex Hahn

[Bill Pentz]

Tim,

The first portable shop vacuum cyclones started appearing on people's web pages back in the early nineties, so OAS by no means pioneered these units. Jim Halbert shared a fairly nice design with needed parts including stand alone vacuum motor back in about ’98.

In terms of that 1.64 cone length to cyclone diameter ratio, I honestly thought the 3 times cone length would be better until some actual testing was done. The agricultural research showed a 3 times cone length worked best and it does with a cyclone having a horizontal inlet. With a horizontal inlet all the air in the cyclone spins waiting for gravity to pull the dust down. There is so much turbulence in spinning that whole air mass horizontally that airborne dust particles 30-microns and smaller mostly stay airborne. A 30-micron particle is about one third the thickness of a coarse human hair. Tilting the inlet and smoothing the airflow can force the airflow to drop the fine dust. The testing that a number of universities and a few medical schools have done on my design showed its 1.64 cone length to cyclone diameter does a five times better job of dropping the fine dust.

Dexter,

I've seen far too much to be a fan of Oneida Air Systems, so decline to comment.

Bill

[Chris Padilla]

Bill,

Lemme know when you are in the Bay Area; you can check out the DC I put together when you were partnered up with Mr. CE.... Keep up the good work; lottsa folks do appreciate it even if they don't say. It is easier to criticize sometimes than give praise. You are obviously a stubbon man--keep on being stubborn!

Cheers...and Happy New Year!

[Eric Haycraft]

Bill, in your opinion.. for a closed attached garage shop would this be an acceptable solution:

clearvue cyclone ~1000 cfm
2 wynn filters vented inside
100 cfm air to air heat exchanger with intake near DC and blowing from the opposite side of the shop. Setup to maintain slight negative inside pressue (since my garage attaches to my house).
I think that I would rig up the heat exchanger to a motion sensor to always run + add an hour or so of runtime after the garage/shop is empty.
DC dumping directly outside is not an option since I am in a townhouse and have an unheated garage in minnesota. brr.

Any improvements would be greatly appreciated..but I am looking for the best setup that I can find that stays around 2k.

[Bill Pentz]

Bill, in your opinion.. for a closed attached garage shop would this be an acceptable solution:

clearvue cyclone ~1000 cfm
2 wynn filters vented inside
100 cfm air to air heat exchanger with intake near DC and blowing from the opposite side of the shop. Setup to maintain slight negative inside pressue (since my garage attaches to my house).
I think that I would rig up the heat exchanger to a motion sensor to always run + add an hour or so of runtime after the garage/shop is empty.
DC dumping directly outside is not an option since I am in a townhouse and have an unheated garage in minnesota. brr.

Any improvements would be greatly appreciated..but I am looking for the best setup that I can find that stays around 2k.

Eric,

My recommendations:

Budget & Once in a While Woodworkers:
(Except those who work indoors or in basements).

1. Buy and use a good 3M 7500 dual cartridge mask fit to your size face. If you are a turner, have a thick beard, or have sensitivities the Trend Airshield seems to be the best powered respirator available for its price. This mask goes on before you start making fine dust and stays on until you have thoroughly cleaned out your shop. If you come back on following days before you clean up, you need to wear the mask.
2. Put and consistently use a big fan in an open doorway. That fan goes on and stays on for the rest of the day anytime you make fine dust.
3. At least monthly open all up wide, put on your respirator mask, turn on the big fan in the doorway, and thoroughly clean out your shop. I’ve used both my air compressor and leaf blower to do this. Then let the shop air settle at least overnight before taking off the mask if you stay in the shop to work.
4. If a door connects your home to your shop put a bathroom vent fan in your shop that turns on when you turn on your shop lights. This will create enough negative pressure that you should not have big blasts of dust going into your home.
5. Wear at least an apron and if the dust cloud is going to be thick seriously consider a jumper, scarf and hat that stays in the garage.
6. Use any decent 1.5 to 2 hp dust collector with a 10’ long 6” diameter flex hose going right to your tools. Even if you neck down right at your dust collector and your tool you will still get better airflow with that bigger pipe.

More serious woodworkers and home shops:
(I think anyone who does lots of woodworking or anyone who does woodworking in their homes or basement shops needs to provide good fine dust collection)

1. Respirator Mask - Buy and use a good 3M 7500 dual cartridge mask when making fine dust. If you are a turner or have sensitivities the Trend Air shield seems to be the best powered respirator available for its price. This mask goes on before you start making fine dust. If you have good fine dust collection where you don’t see any dust spray from your tools you can then take the mask off. Most of us end up even with good fine dust collection, still have a few tools that just cannot be tamed like my 7” sidewinder. It will throw dust all over the shop. After making fine dust any time you go back in the shop you should wear the mask and keep wearing it when in the shop whether or not you are making fine dust until you have thoroughly cleaned out your shop. The problem is we only need a couple of thimble fulls of previously made fine dust which is easily launched by shop airflows to make our shop air very unhealthy.
2. Fan – I prefer to always have a fan running in an open doorway when weather permits.
3. Hoods - Upgrade/add appropriate hoods on your tools. Our hoods need to contain the fine dust while blocking and trapping any airflows greater than about 50 FPM. A 50 FPM airflow is about the speed of a soft breath. If the hoods don't control the dust and breezes, we will have poor fine dust collection even with huge dust collector or cyclone blowers.
4. Tool Ports - You also will need to upgrade your tool ports. Most tool port sizes are 4" for good chip collection. For good fine dust collection we move more air so need bigger ports. The port size should match the ducting size. A 6” duct drown drop should go into a 6" port and a 7" down drop should go into a 7" port. If you have a machine that has more than one collection port, then the cross sectional area should add up to the area of the down drop. For instance the minimum 6" diameter duct needed to support the airflows needed for good fine dust collection has a cross sectional area of 28.27 square inches. So the areas of our two ports added together shoulld be 28.27 square inches plus or minus about 10%. The following table can help you add up the areas of two different port sizes. The green blocks show the only combinations that will work with 6” ducting.
   
   
5. Ample Air Volume - If you work the resistance numbers and do actual testing, the better Jet and Delta 1.5 and other real 220V 2hp dust collectors will do an excellent job of “chip collection” leaving us with clean looking shops, but these are not ample to do a good job of pulling in the fine dust. If you want the really fine dust collection ample to pass an EPA test (medical recommendation), you need to move 1000 CFM from most large stationary small shop tools. You need either a standard pressure blower that moves 4000 FPM air velocity in our ducts with all 7” ducting going right to each tool, or an oversized impeller that will move 5100 FPM in a 6” duct to provide that same 1000 CFM. I’ve engineered enough extra capacity into my blower designs with the 15” impellers they will handle the 1000 CFM airflows using 6” duct. With this more powerful blower design you get to use the much more available, less bulky, and less costly 6” duct. The fan tables show to get the airflow needed anywhere in a 2-car garage sized shop with 6” ducting show for good fine dust collection against normal 2-car shop pressures we need a 3 hp dust collector or 5 hp cyclone.
6. Venting Outside
   
   1. If you live in the country and don’t work with woods like walnut and many of the exotics that are toxic and can kill other plants/harm livestock, blow this whole mess far away from your home and forget filtering.
   2. If you live in a mild climate, just about any 5 hp cyclone with 7” ducting will separate good enough to blow the fine dust away outside without any mess unless you let your dust bin get full. Then all blows right through.
   3. No matter where you live I’d like you to install a valve that lets you blow the fine dust away outside whenever weather permits.
   4. Makeup Air - If you blow outside I suggest at least a 14” diameter or larger air hole or open door/window for makeup air without whistling or chance of sucking carbon monoxide backward from your vents and flues into your shop.
   
   
7. Filtering - If you vent inside you need to filter with a fine enough filter to get rid of the fine dust. Most small shop advertized “fine” dust collector and cyclone filters need months to years to build up enough cake of dust in the filter pores before they will actually provide their advertized filtering level. Meanwhile our lungs get to filter off the fine unhealthiest invisible dust. My respiratory doctor recommends you use filters tested when clean and new as required by ASHRAE for indoor filters. I also recommend protecting these fine filters from massive dust loading by not just using a cyclone, but a finer separating cyclone.
   
   1. Filter Rating - Those with no known problems can do well with the less expensive 0.5-micron filters. Those who are more concerned or have a history of problems need to wear a good mask when woodworking and should use the 0.3-micron or finer filters. The HEPA standard requires each filter be separately tested and provide 99.97% filtering efficiency on all particles sized 0.3-microns and larger. The cost for individual filter certification is high, so I think buying a good quality filter that uses HEPA grade filtering material is ample.
   2. Filter Games - Most small shop cyclone vendors say you only need to clean your filters every 3 to 6 months. But if you look closely on their web pages they admit their filters pass much larger particles than advertized until their fiilters season. Seasoning means building up a permanent cake of fine dust in the filter pores that does not come out with normal light cleaning. We get up to twenty times larger particles going through a fine filter that is clean and new compared to one that is "fully seasoned". If these filters were outside and the fine dust just blew away this would not be a problem. Instead these filters are indoors and this dust lingers for months to years. Passing most of the finest 10-micron and smaller dust particles until they these filters fully seasoned will let vendors claim high filtering levels and let them sell much smaller filters. The better the filtering level, the large our filter needs to be to avoid too rapidly plugging. These open filters leave us using our lungs to do the fine filtering for the six months to two years it takes for their filters to season.
   3. Filter Cleaning - Worse, most of our filters wear out before they ever fully season. As our filters get dirty the air pressure rises enough to force the fine sharp particles to cut and tear their way through the filter pores leaving us with wide open filters. Cleaning does the same thing but faster. Most small shop woodworkers are a touch obsessive about how well we do things. Instead of a light shake or few taps we pull out 100+ PSI shop vacuum or our 120+ PSI air hose and really clean our filters. One heavy vacuuming or spray down can trash a new set of filters. These high pressure airflows really force the fine sharp particles to tear their way through the filter matrix.
   4. Filter Sizing - Size your filters appropriately whether a bag filter or cartridge. If you read over the filter sizing guidelines and the engineering notes from Donaldson Torit, one of the biggest names in filters in the U.S. if not the world, they recommend a maximum airspeed of “clean indoor air” through the filter of no more than about 10 FPM. We can take our 1000 CFM divide by 10 FPM and come up with a minimal area of 100 square feet of filter. If you dig further into the engineering notes they provide formulas that require us to increase the area based upon what particle loading. With my cyclone design and medical school verified separation levels, we still need about 250 square feet of filter area. With other cyclone designs that put five times as much fine dust into the filters you need a lot more area. Additionally, in the fine print on the Donaldson Torit engineering recommendations, they recommend using twice as much filter area as the minimum. Doubling the filter area will cut filter resistance by a factor of four, double the time required between filter cleanings, and make our filters last four times as long. That comes out to 500 to 600 square feet of filter area for my cyclone. Most small shop dust collectors have less than 120 square feet of area and really need over 600 square feet at typical dust collector dust loading. This means dust collectors need four times as much area and other cyclones far more as well. For what it is worth, this is why so many end up very unhappy with their dust collector cartridges needing constant cleaning.
   5. Filter Type - A pair of the big Farr or Farr compatible 270 to 300 square foot blended poly paper fiber filters work great on my cyclone design, but the all poly filters that cost more than twice as much are a better buy. The all poly spun bond filters provide the same level of filtering with half as much surface area, so we only need half the total filter area. Unlike paper poly blended filters that get tossed when their filtering gets bad, we simply wash the poly filters to restore their full filtering ability. We can wash the all poly filters three to five times before they need replaced. The all poly filters are also more forgiving than the light blended filter material during cleaning.
   6. Filter Sources - I bought my original fine filters from Donaldson Torit directly, but they that firm was not well setup to deal with hobbyists and small orders. There were payment issues and shipping damage. I now buy my filters from Wynn Environmental. Wynn Environmental is a family run business that between Rick and Dick know more about filters than I know about cyclones. Most purchase a pair of their 9L300BL filters, but if you can afford the extra cost I prefer using a pair of their all spun bond polyester filters, model number 28B140SBOL.
   7. Filter cleanout - Most of us make little cleanout boxes or drums below the filter tree from either a wooden box or from galvanized metal. Wynn has an exploded picture of a box arrangement. Shape is not that important, but a good seal is. I made mine out of galvanized steel with a wooden donut in the top and bottom with a 4” outlet on the side. I have an airtight cap to cover on that 4” outlet. To clean the filters I remove the cap, connect a long 4” hose going outside, turn on the cyclone and tap the filters a bit. Instead of tapping you can either blow on the outside of your filters with your vacuum set on blow or blow down with a compressor hose with the pressure set to 40 PSI or below. Clear Vue Cyclones come with some detailed instructions to build and setup your filter cleanup box.
8. Cyclone – To minimize our filtering overhead we need a good fine dust separating cyclone that both moves enough air to collect the fine dust as it is made and provides a very light dust loading on our filters. Don’t get fooled by vendors that provide filters that are wide open and freely pass the finest unhealthiest dust then say they provide a good fine dust separating cyclone because you rarely need to empty filters. I recommend either building my cyclone design from my web pages or buying the same 18” cyclone design from Clear Vue Cyclones with the 5 hp motor and 15” impeller. This will also let you use 6” instead of 7” diameter ducting.

[Tim Marks]

Makeup Air - If you blow outside I suggest at least a 14” diameter or larger air hole or open door/window for makeup air without whistling or chance of sucking carbon monoxide backward from your vents and flues into your shop

Actually very important to avoid damaging your house. People with "Whole House Fans" sometimes run into problems with this. Unless you open a door or a window for makeup air, you can end up sucking air laden with moisture in through cracks in the siding, leading to mold damage inside your walls.