# Is Bill Pentz dust collector safety exaggerated?



## RichardDePetris (Oct 14, 2013)

I'm considering building my own dust collector. I found several parts that I scavenged and one of them is a HVAC furnace blower from a neighbor who replaced their HVAC system. As I understand it, the RPMs are too low to create enough static pressure, so I will have to replace the motor with a higher speed AC motor. I have quite a collection of 1/2 HP to 1 HP motors I can use. The squirrel cage will have to go, leaving me with only the housing which may work for housing the impeller and motor.

I've been reading all kinds of resources online and was very excited about this project until I stumbled upon Bill Pentz's site. He is supposedly an expert on dust collectors and has extensive information on how to build one. Unfortunately, he really scares the crap out of me for not having a proper one and then scares the crap out of me if I don't build it according to his specifications, which costs as much or more than an decent dust collector.

His specifications states emphatically that you only use a steel impeller by his recommended manufacturer (http://billpentz.com/woodworking/cyclone/blower.cfm). Plastic can't stand up to the rigors of dust collection and will eventually fall apart, especially when hit by debris. An aluminum is far worse-as good as using a plutonium one. If a hard object hits the impeller, it can explode into shrapnel and kill everyone and destroy everything in sight. Worse yet, if a ferrous metal hits it, it can spark and start a thermite chain reaction, turning your dust collector into a hot molten core of metal burning its way through the concrete foundation where it will hit the ground water and exploding into a giant mushroom cloud, scorching the neighborhood with days of darkness, fallout and centuries of toxic ground water.

Obviously, I am exaggerating here, but is Pentz exaggerating also? Is there any validity to these spectacular claims? Can you get a thermite reaction in a dust collector? Can a nail cause the impeller to break apart into pieces of high velocity metal? They are a bit over the top, considering that I've never heard of anything like this happening before. Moreover, it makes me wonder what horse Mr Pentz has in the game considering he designed a commercial dust collection system with his name on it.


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## intelligen (Dec 28, 2009)

Bill Pentz strikes me as a bit of a crackpot. Although much of what he says is probably true, a lot of it is written like an infomercial and seems exaggerated for dramatic effect. I would find his claims a lot more believable if he had gone to the effort of writing actual research papers and getting the published in respectable journals, even with all the peer-reviewed journal scandals.

That said, inhalation of wood dust is hazardous, and the best way to protect yourself from dust inhalation is to wear a good P100 respirator with replaceable filters.

As for the specs of his dust collection designs, if you put a cyclone or separator before the dust collector, the cyclone will catch the debris before it ever gets to the impeller. It would be nice if he just summarized his findings and said, "here are the plans for a system that will work for anyone," rather than forcing everyone to read his entire website and understand every little detail that affects the performance of a system.


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## djg (Jun 24, 2012)

Bill sounds like a crack pot but his website is not spreading propaganda. Everything he says is true. Capturing dust at the source, moving lots of air, vacuums for some situations, dust collectors for others…all true. Now the health effects…all true. Most of huge effects are irreversible. Just to let you know, I work as a medical physicist at a cancer centre. The cases of lung and head and neck cancer (nasopharyngeal cancer, oroparyngeal cancer, etc) That I have seen linked to people that worked in industries where particulate matter is the main hazard is phenomenal.

I don't think bill is exaggerating. I do think he is passionate about getting the word out given his own health situation. Good for him. But I do agree that it would be nice to provide a simpler summary as stated by Rob.


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## hhhopks (Nov 22, 2011)

Fine dust is potentially explosive. Make sure your system is grounded to reduce electrostatic build up. Grounding of your duct work will also reduce the likelihood of getting shock. At least this part is relative inexpensive.


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## Pezking7p (Nov 17, 2013)

The thermite thing is exaggerated.


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## wapakfred (Jul 29, 2011)

I see Pentz as a truly knowledgeable guy that did a chit load of work to get some facts out about DC. You would be wise to follow his advice as much as possible.


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## English (May 10, 2014)

Those of you out there that don,t have COPD may feel Bill is a crackpot. But for the ones like me with COPD that have followed the work of Bill and build a system to his specs, breath much better. Before I put in my system, the only way I could work in my shop was with a respirator, not a dust mask. Now I can use any of my tools except my hand sanders with out any mask.


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## hotbyte (Apr 3, 2010)

I've not studied his site in great detail but his ideas and design seem to be spot on for an ideal DC setup that I'm sure every woodworker would love to have. Some of his presentation does come across as a little Chicken Little'ish or, as mentioned, infommercial'ish.


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## rwe2156 (May 7, 2014)

No, Pentz is not a crackpot. Yes, Pentz is the guru of DC. I tried to wade through the technical details when I designed my system, but ultimately had to give it up and just try to understand the basic principles. I've talked to some guys with huge shops (one has a 10HP cyclone) and they've never had a fire or explosion or anything close to it so I think that part is a little overblown. Remember, he's doing this for a living.

You said it right. His systems are commercial systems really for industry and OSHA regs. For the average ww'er like most us, IMO they are WAY over the top. I see alot of guys investing $3-4K in a DC system but they are still going to have to wear a respirator when they run MDF through their TS, so what have they gained?

Most of us aren't really looking for true "dust" collection, ie, a uber-DC system that traps 99% of the dust. We are looking to keep our shops from filling up with shavings and sawdust (at least I am). We can keep our lungs clean with a $40 respirator, not a $4000 DC system.

As far as your system, you don't say what machines you have, but regardless, I would discourage using an HVAC squirrel cage fan. It just isn't going to get it for DC unless your system is extremely small. If money is a big factor, you can pick up a 2HP unit from Harbor Freight and just use the blower. You can build the Pentz cyclone or do what I did and save the time just buy a super dust deputy.


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## Crank50 (Jan 31, 2014)

More specific to the plight of the OP, you cannot use the housing of the squirrel cage blower either. It is too wide. It is designed for a large volume of air movement with relatively low pressure (low static). That is the exact opposite of what you need.

I think Bill Pentz, to answer your other question, means well and is grounded in basic truth and adherence to the laws of physics. But I do personally think he is biased toward his own products and skews his recommendations toward them. Not sure if that is all a bad thing, but it just hurts his credibility in my opinion.

I have designed and built industrial pollution control equipment and systems for much of my career which spans over 40 years. Some of his products are not the best out there either. On the other hand, true industrial quality dust control equipment would be completely out of reach for any but the most affluent of us. A typical industrial dust collector would usually start at around $5000 and go up quickly from there.


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## timbertailor (Jul 2, 2014)

If you keep asking enough people, someone will tell you what you want to hear.


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## ksSlim (Jun 27, 2010)

When I was still working for a living, someone gave Bill my contact info.
At that time I supervised the Metrology lab in support of experimental flight test.
We calibrated sensors to be installed on the experimental aircraft.
A few simple sensors, would help prove line losses in your system.
We also used various calculations to properly capture chips and fine dust.
A Winn canister filter will ease back pressure on your equipment. (move air more efficently )
90 degree connectors usually decrease efficiencies by 28 to 32 percent 
Its better to use 2 45 degree tube connectors in lieu of one 90 degree.


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## TheWoodenOyster (Feb 6, 2013)

I don't think Bill Pentz is a crackpot. I think he got burned by fine dust and is trying to help others not end up in the same situation. I agree that the whole exploding shop thing is probably a little over the top. The lung protection portion is not overkill if you want REALLY good dust collection. His view and designs are made to give the best dust collection situation possible. That isn't feasible for most of us, so we just get as close as we can. A respirator is the answer.


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## intelligen (Dec 28, 2009)

To clarify my earlier statement, "Bill Pentz strikes me as a bit of a crackpot," if he just gave the facts without all the narrative, he would not come across as a crackpot. It's the anecdotal infomercial tone that really dings his credibility. If someone wrote a Cliff's Notes version of his website and cited research papers to support Bill's claims, his work would be a lot more helpful to a lot more people.


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## CharlesA (Jun 24, 2013)

My non-expert opinion. Pentz is obsessive. That is a gift to those of us who want to learn, since he will examine everything. For many of us, that means we can learn from him without following everything he says absolutely.


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## AZWoody (Jan 18, 2015)

When setting up my shop the first time, I read his pages and found him knowledgeable but prone to exaggeration and even contradictory.
He seems to be a guy who took the "guru" title and ran with it. I think the crackpot tag is somewhat fitting though but one of those crackpots who mostly got it right.

To do everything the way he says, means you'll have an industrial dust system for a small hobby shop and that's just overkill for most. 
It also depends what kind of machines you run and what you think you'll be doing in the future.

I'd say get as close as you can to his recommendations as you can afford, and if possible, push the budget as much as you can. The rest is going to have to be done to fit your own unique requirements and your own health requirements. Some are more susceptible to dust and types of lumber than others.


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## WoodNSawdust (Mar 7, 2015)

I suspect that Bill Pentz in knowledgeable in what he says. I can't prove it since I don't have any expertise in the field of dust collection.

As others have said or implied there is a lot of information to wade through and it would be a lot more useful if there were some simple guidelines and plans to use.


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## RichardHillius (Oct 19, 2013)

Nothing Bill Pentz says is new. It's all things the commercial dust collection industry has known for years. He just brought to light a lot of these practices to smaller home shop's where before they were only really understood by a small number of companies that specialized in building these kinds of big systems for commercial use.

The question at the end of the day is, Do you need to consider all these factors in a average home shop dust collector? I think that's a personal value decision more than anything else. Personally I am glad the information is out there however I feel there needs to be room for people to do woodworking safely without spending enormous amounts of money. I think there are things people can do to make their time in the shop safer when it comes to dust without going to the extremes Bill's system would indicate. It's been awhile since I read his site but I do tend to recall him talking about other options like dust masks as well.

I guess at the end of the day while I appreciate Bill's work in pulling together the information and I really like ClearVeu cyclones I hate to think his work might cause someone to not try woodworking for fear that they would have to spend enormous amounts of money to do woodworking safely. I just don't feel that's the case.


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## brtech (May 26, 2010)

I've struggled with Bill's information. Most of the facts I think are beyond reproach. The prose is over the top.

The question is what to do.

I think if you want to be safe without a respirator, you need what he says, 5HP, properly designed cyclone, 6 inch ducts, wide sweeps or two 45s with a short straight section, and little to no flex. Period, no ifs, no buts.

My dilemma is what do you do if you can't afford that. I think you have three choices:
1. Wear a respirator all the time, and use a cheap DC to clear the chips. No cyclone, no baffle, just clear the machines from clogging up.
2. Put in a system that has insufficient suction, but decent filtering, and use a respirator when generating lots of dust (not chips). For sure, you will inhale bad stuff, because dust is generated in nearly all woodworking power tools. Accept that it's not really safe.
3. Do what he says

I think the school of thought that more is better is only partially right - there is a minimum where all you get is option 1 (chip clearing), and not much health benefit. Once you have somewhat decent suction, and adequate filtering, then the lack of suction allows some dust to escape the system, but until you get to that, you only are clearing chips. So, for example, adding a rigid 4" duct system to an HF 2HP DC doesn't do much if you haven't upgraded the filter to .5 micron. If you have got decent filtering, then things that improve suction help. The big, big caveat is that things that improve separation DO NOT IMPROVE HEALTH. And specifically, they usually cause a loss of suction, and thus poorer dust control. That's the mistake I see people make. They want a poor cyclone or a Thein baffle because they like the fact they have to clean the filter less often, and dumping the bag on the cheapo DCs is a PITA. This DECREASES suction and increases dust in the air. You should always improve your suction first, then worry about separation.

A 5HP motor with a decent impeller, good ducting, a good filter and a poor cyclone will keep you safe without a respirator. You will have to clean your filter more often. Bill bashes poor cyclone design, but most of the problems he seems to find are related to separation efficiency and not insertion loss.

I'm in my second camp. I have the HP 2HP DC, a Wynn filter and a Dustright expandable hose. I use my respirator when sanding or sawing MDF and other larger dust causing activities. I have an air filter that is on whenever I'm in the shop and for an hour after I leave. I don't consider it safe, and I'll get a 5HP DC at some point. I have to check my filter often, but it's not that hard to clean it out. I've considered adding the Thein baffle, but decided that the decrease in suction is not a good idea.


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## wormil (Nov 19, 2011)

The hazards of wood dust have been known since the early 1800's, at least, and modern-ish dust collection systems with separators were not uncommon by the mid-19th century. The only reason were are "rediscovering" those hazards are because industry pretended not to know about them.


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## NoSpace (Jan 2, 2015)

Wow, this is a popular subject lately. One more post and I'll move on…

There are a few problems with Pentz's line of argument and there is an infomercial quality to the whole thing, but then again, there's a lot of good information there too. Let's face it, it's good he's scaring people because otherwise they wouldn't take it seriously.

But consider this: all of this research he did was like 20 years ago. He talks about going into small shops and finding these horrible air quality problems and talks about how these problems occur and how hard they are to get rid of. But OK, how was this research done? What drove me crazy above all else reading his site is I kept waiting to get to the part where he explained how to go about measuring the dust problem in your shop but that never comes. There's substantial conjecture and tenuous reasoning: a thimble full of dust can cause an air quality test to fail, you don't have an exhaust system like a big shop, and so your shop is doomed.

Twenty years ago, there probably wasn't a realistic way to measure the air quality in your shop short of a 10k Fluke meter. Now I'm going to sound like an infomercial and mention the Dylos 1100 pro for 260$ for the third and last time tonight that will tell you exactly how bad of a small particle problem you have. It's a simple and cheap matter to get the air in your shop cleaner than anywhere else you'll likely find yourself on a given day as you will find, once you have a tool to measure the dust objectively.

The hard and expensive part is to have the air clean in close proximity to the tool in real time as you use it. As others have mentioned, the p-100 mask for <40$ solves that problem.


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## ChrisBarrett (Jul 4, 2015)

I just read over a big chunk of his website. He would do well to get an editor. Very very very very repetitive. Yeah we get it, woodworking creates fine dust. More words does not mean more information.


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## Hopdevil (Dec 13, 2009)

> If you keep asking enough people, someone will tell you what you want to hear.
> 
> - timbertailor


Great Quote! Thanks


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## REO (Sep 20, 2012)

thermite is a mixture of fine particles of aluminum and iron: you will not create a thermite reaction with one strike or several for that matter of the two in solid form. you wont get a spark from aluminum striking steel. I used to design and install industrial Dc systems up to 350 hp and multiple fans. Although conceptually possible I have never heard of a sawdust explosion from a spark in a dust collection system or bag house. I have heard of bag house explosions caused by smoldering lumps of sawdust breaking loose from faulty bearings and grease and cigarettes sucked up into the collection ports but not that were actually traced to a spark from a nail or bit of metal, or a static spark in a system. The following clip was actually challenged by myth busters because try as they might they couldn't figure out how to get sawdust to ignite in a cloud. Chad set them straight and they finally succeeded. 
sawdust bomb

This is well presented:
spark boom possible?
most of the small DC systems run the debris through the fan then to the filter. A proper separator will save the fan form impacts from chunks that could damage them. over the years I have had several fans blow up for several reasons, from 1 hp up to 125 hp. catastrophic but no material got shot through the housing. some pretty good dents though! the speed might be there but the velocity is lost because there is no chance for a direct perpendicular impact at velocity.

The squirrel cage blower just wont work for several reasons. regardless of modifications.


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## exelectrician (Oct 3, 2011)

REO ,, Thanks for the sawdust bomb link . Awesome!!!


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## Pezking7p (Nov 17, 2013)

From my personal experience with thermite reactions, you will not ignite any in your dust collector. And the thermite reaction he is referring to is with aluminum and rust, not iron. Typically these reactions are very hard to kick off unless you're using powders or have extremely high heats.

Odds of demolishing an aluminum impeller are pretty low.

Anyone who has worked in dust can confirm its not good for you. It's not going to kill you but it's certainly not helping matters.


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## marvinlee (May 28, 2012)

> I m considering building my own dust collector. I found several parts that I scavenged and one of them is a HVAC furnace blower from a neighbor who replaced their HVAC system. As I understand it, the RPMs are too low to create enough static pressure, so I will have to replace the motor with a higher speed AC motor. I have quite a collection of 1/2 HP to 1 HP motors I can use. The squirrel cage will have to go, leaving me with only the housing which may work for housing the impeller and motor.
> 
> I ve been reading all kinds of resources online and was very excited about this project until I stumbled upon Bill Pentz s site. He is supposedly an expert on dust collectors and has extensive information on how to build one. Unfortunately, he really scares the crap out of me for not having a proper one and then scares the crap out of me if I don t build it according to his specifications, which costs as much or more than an decent dust collector.
> 
> ...


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## marvinlee (May 28, 2012)

> I m considering building my own dust collector. I found several parts that I scavenged and one of them is a HVAC furnace blower from a neighbor who replaced their HVAC system. As I understand it, the RPMs are too low to create enough static pressure, so I will have to replace the motor with a higher speed AC motor. I have quite a collection of 1/2 HP to 1 HP motors I can use. The squirrel cage will have to go, leaving me with only the housing which may work for housing the impeller and motor.
> 
> I ve been reading all kinds of resources online and was very excited about this project until I stumbled upon Bill Pentz s site. He is supposedly an expert on dust collectors and has extensive information on how to build one. Unfortunately, he really scares the crap out of me for not having a proper one and then scares the crap out of me if I don t build it according to his specifications, which costs as much or more than an decent dust collector.
> 
> ...


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## marvinlee (May 28, 2012)

Bill Pentz is the leading authority known to me on dust collectors and their design. The actual risk faced by part time woodworkers is, however, very difficult to pin down. For example, here is a relatively recent study from the Northwest where I live. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3184400/ it shows no significant risk from hobbiest woodworking. The missing element in many databases is that not all relevant factors are screened for. For example, the direct exposure time for individual dust exposures, the frequency of those exposures, the kind of wood being processed (the study contemplated soft wood dust) and many other issues are seldom known. However, the study made me reconsider what might have become excessive concern.


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## Joel_B (Aug 14, 2014)

I decided to get a Dylos DC1100 particle counter. It can tell you when there is or isn't a problem.
Have not used it much in the shop since I have not been doing much woodworking lately, but inside I get wildly fluctuating levels I think the numbers go way up when I am cooking in the kitchen. I expect it will be very useful in the shop. I wear a 3M respirator when working in the shop. I only have a shop vac and thinking of getting a cyclone for it and go from there. I think Bill Pentz has a lot of good information on his web site but its kind of a conflict of interest to talk about his unfortunate extreme situation and then be selling very expensive equipment that claims to solve it.


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## marvinlee (May 28, 2012)

> I ve struggled with Bill s information. Most of the facts I think are beyond reproach. The prose is over the top.
> 
> The question is what to do.
> 
> ...


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## marvinlee (May 28, 2012)

I've recently read, and will post reference if I find it, that ceiling mounted dust collectors actually worsen air quality while running due to mixing up air and dust throughout the shop. The advice was to set the collector to run for a time after the shop has been vacated and then to work later when the remaining dust has settled to the floor, leaving the breathing air relatively clean. I have an open mind on this, but will still likely run the ceiling collector and a face mask when generating substantial amounts of dust.


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## wormil (Nov 19, 2011)

Marvin, you need to get a handle on that quote function. I have no idea if you are empty quoting or replying or what.


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## wapakfred (Jul 29, 2011)

Marvin, I see great value in the ceiling air cleaners, none of that value is related to respiratory health. I still see the air cleaner catching the dust after it's has already got into your lungs; I fail to see how it can help with that. It does have great value in keeping ambient dust contained in the shop….always a good thing. But the best plan of attack is to catch at the source; the downfall of that is that even a world class system can't get it all, try routing MDF to see what I mean. I've never heard they make shop worse, though my general practice is to turn mine on when I leave the shop and let it run a few hours.


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## OggieOglethorpe (Aug 15, 2012)

I think he's a tad obsessive and dramatic, but some of what he says is true.

One thing that gets lost a lot in heath and safety issues is exposure level. It's one thing to be a hobby woodworker who uses a table saw a few hours a week, but yet another to work in a factory running a wide belt sander all day long, 5-6 days a week, with a 30 minute lunch break.

As far as fire hazards go, don't smoke in the shop and don't sharpen tools on machines with dust collection… Nothing will ruin a day faster than a cigarette butt or glowing steel particle in the tubing. It may not even ruin today, simply smoldering away to ruin your tomorrow…

And of course, if you smoke, worrying about inhaling dust might be putting your initial efforts in the wrong direction.


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## clin (Sep 3, 2015)

> Marvin, I see great value in the ceiling air cleaners, none of that value is related to respiratory health.
> - Fred Hargis


This makes no sense to me. The room filters keep the dust level lower while cutting than if they weren't there and lower it more quickly after cutting. How can that not be better for your health.

Now, I would agree that if you have your face stuck right down where the dust is coming out, it's little immediate help that the air gets filtered away from you. Though even then, as soon as you step back from the tool, the air is going to be cleaner with the filter than without.

I think it would be unusual to have your face that close to where the dust is being thrown out, and even without filtering, just having something moving air would help to lower the dust concentration near the tool.

My own experience with a Jet filter and using a Dylos meter is that the ambient dust levels are lower while cutting with the filter running and that they drop more quickly after cutting. Also, as I move around the shop and kick up dust, the room filter keeps the level lower. According to the particle meter, ambient dust levels are lowered under all conditions when running the filter.

As you mentioned, I would agree that capturing the dust is the optimal situation, but for dust in the air, a room filter reduces the ambient level and presumably this would be a health benefit.


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## wapakfred (Jul 29, 2011)

Your point is about how much…to me any at all is bad, and the damage can start with very little. Nevertheless, we can agree to disagree.


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## bbasiaga (Dec 8, 2012)

I'm kind of passionate about the idea that people can get in to this hobby, and do good work without spending thousands and thousands of dollars on tools. The issue I have with the Pentz dust collection stuff, much like the issue a lot of folks have with the Sawstop marketing, is that it is very totalitarian and ignores other control methods for the exposure. Also, as OggieOglethorp states, it works on the assumption that breathing one spec of dust once is just as bad as breathing it all day every day in a production environment. The data is not there to support that either way. (note that there are dusts that risky, like asbestos, but natural organic dusts are not considered to be in that same category)

There is certainly risk in breathing in dust, and it makes only good sense to put some exposure controls in place. For about $30 you can get a nice respirator form Home Depot and never breath a spec of any wood dust in your shop. Ever, as long as you wear it. If you get the right size, and learn how to properly adjust it, they are very comfortable and after a while you won't know they are there. Half the time I forget about it until I try and blow some dust off of something and can't! (So I guess you have to add $5 to the cost for a little air puffer for your pocket).

You don't need $10k in dust collection and a new electrical service to your shop for a DC system. If you don't want to wear the respirator, that may be what it takes. In the middle, you can work outside, work in a well ventilated area, have some dust collection and wear a respirator, add an air cleaner, etc…

How much of a barrier of protection you need depends on how much risk you are going to tolerate. Some folks will never ride a motorcycle because of the risk. Others will never wear a helmet while they ride because they don't value the risk the same. If wood dust is too much of a concern for you, then don't do this hobby. That is your choice. But if you think you can't do the hobby because you can't afford to control dust exposure, you are wrong and the person who told you so has done a great disservice to you and the craft by saying so.

-Brian


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## marvinlee (May 28, 2012)

> Bill sounds like a crack pot but his website is not spreading propaganda. Everything he says is true. Capturing dust at the source, moving lots of air, vacuums for some situations, dust collectors for others…all true. Now the health effects…all true. Most of huge effects are irreversible. Just to let you know, I work as a medical physicist at a cancer centre. The cases of lung and head and neck cancer (nasopharyngeal cancer, oroparyngeal cancer, etc) That I have seen linked to people that worked in industries where particulate matter is the main hazard is phenomenal.
> 
> I don t think bill is exaggerating. I do think he is passionate about getting the word out given his own health situation. Good for him. But I do agree that it would be nice to provide a simpler summary as stated by Rob.
> 
> - djg


Those are very bad diseases and I understand your concern. However, without taking into account the patients' past smoking history, age, and additional risk factors, one can hardly be sure what caused the various problems. And, we don't hear much about the uncounted millions who face those, and many other, risk factors and live long, healthy lives. Further, the intensity and duration of risk exposure in hazardous occupations may not typify the risk exposures of part time woodworkers.


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## JohnDon (Mar 14, 2015)

My take on the venerable Mr. Pentz's work is this:
1) He makes a compelling argument for the risks of breathing small dust particles.
2) It takes a high air flow for a cyclone to remove small particles.
3) For high air flow, you need a powerful (5 hp) impeller to get good dust separation.

In my mind, what he stresses is that "trashcan separators", or less than perfect cyclone designs do a bad job of removing small dust particles. What he seems to downplay is that a good canister filter (like a Wynn) can also do a good job of removing small dust.

My conclusion is that for a small shop, you can get very acceptable dust collection with a moderately powered (say 1 to 2 hp)- and priced- DC by using a good filter (or vent outside, if an option). Add a less than perfect (practical) cyclone or Thien separator. While it won't remove all the particles, it will remove most of the dust so it will 1) trap particles/chunks/metal which might damage the impeller, and 2) reduce the dust load on the filter, so it won't clog and need cleaning so often, and will maintain adequate air flow.

I also agree that a ceiling mounted air cleaner is a health benefit. I can't see the argument that it worsens air quality by stirring up dust. After all, any air it stirs up will be sucked up by the cleaner, and therefore filtered. In a sense, it's also "breathing" air in the shop- that is, competing with your lungs for air flow (and dust!). so, any dirty air that goes through the cleaner is air and dust that won't get into your lungs.

Finally, a good respirator dust mask is the best protection.


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## wormil (Nov 19, 2011)

The dangers of wood dust have been known since the early-mid 1800's and the first dust control systems were invented at that time. For most people, money and space will be the limiting factors to dust collection. Given unlimited resources, I'm sure the majority would opt for best DC money could buy.


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## clin (Sep 3, 2015)

> My take on the venerable Mr. Pentz s work is this:
> ...
> 3) For high air flow, you need a powerful (5 hp) impeller to get good dust separation.
> 
> ...


I didn't get that point from reading Bill's site. I think he promotes high powered blowers, not to improve separation, but to get high enough air flow and airs speeds at the tool. If the air speeds are not high enough, the particles have enough speed coming off the tool (table saw blade) to escape the DC and therefore won't get collected.

He promotes the use of cyclones because then you can either exhaust this nearly dust free air outside, or through a Wynn type filter. Without the good separation a cyclone provides, a Wynn type filter will clog up quickly. I'm sure he doesn't recommend a recirculating system with ONLY a separator and no fine filter, like a Wynn.

He promotes good cyclone design because this will minimize load on the system and optimize airflow.

I believe his reason for recommending 3+ HP and higher systems is that these are what is needed to capture the fine dust.



> The issue I have with the Pentz dust collection stuff, much like the issue a lot of folks have with the Sawstop marketing, is that it is very totalitarian and ignores other control methods for the exposure.
> 
> -Brian
> 
> - bbasiaga


As I recall, Bill actually recommends several other things as being better than high power DC. For example, if at all possible work outdoors (still with respirator). Next, use lots of ventilation through the shop. Next, use DC, but exhaust to outside. Using a recirculating DC, with cyclone and fine (Wynn) filter is down on his list.

However, if you are going to recirculate, he has strong recommendations on how to do it well.


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## wgmcg (May 12, 2017)

Setting up a shop in my basement and just read all through the Pentz site, and while I agree that there's some good information there, it's poisoned significantly by his tone. He sounds like an anti-vaxer, or one of those wifi causes brain cancer people.

I'd trust him more if he provided particulate data from various common setups which he claims are inadequate, but cost significantly less to build than the $2k+ systems with his name on them that his website shills. He's a Dylos owner, seems like it would be simple enough data to collect.

The data he does provide seems to obscure rather than clarify, which makes me think he's one of those, "look numbers! Trust me I'm smarter than you!" type of guys. I mean look at his page on the Dylos Air Quality Monitor.

http://billpentz.com/woodworking/cyclone/dylos.cfm

While interesting, its all methodology and no data.

Contrast to this:

https://woodgears.ca/dust/dylos.html


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## TheRiflesSpiral (Mar 20, 2017)

> While interesting, its all methodology and no data.


And no references.

I ran across his site early in my shop planning and the very first paragraph put me off. ("A. Summary" from http://billpentz.com/woodworking/cyclone/index.cfm#index.cfm) He makes no fewer than 8 claims in half of that paragraph, none of which list any kind of source or make reference to the material that would support the claims.

As I read further it's clear that you're just supposed to take his word for it. Maybe he's knowledgeable, maybe he's not, but I don't find him trustworthy therefore I'm not inclined to believe that he is knowledgeable.

His blog is at least a little better due to the graphics having image credits but it, too, is full of "this guy is an expert and he told me this thing so now I'm an expert and you should trust me."

It all smacks of a person who had a medical scare and might be trying to prevent others from having it… or might just be trying to sell cyclones… who knows?

I try to keep an open mind and use the info I can while ignoring what's counter-intuitive but it's a lot of excrement to wade through to get to the valuable bits.


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## Manitario (Jul 4, 2010)

It's interesting reading the comments about Pentz; I'm not sure where some of the anger towards him implied in some of the posts here, comes from. He's a hobbiest, not a professional woodworker, who had some significant health problems and did some independent testing of DC machines. I've never seen an advertisement for his site, nor do I think he makes any money off of it (other than what people donate). Not sure if he makes any $ from Clearvue, but given that he doesn't own Clearvue (and Clearvue is a relatively small company) I'm sure he doesn't make much from royalties. Also, his site has extensive plans and instructions on how to build your own DC, and his website is free, so if he's trying to make money off us, he's doing a pretty poor job.

He mentions that he bought all the testing equipment himself and several different DC's to compare, this was all on his own dime. He also is an engineer, and his testing methods seem reliable, and based on testing methods for DC's and airflow that I've seen in other airflow applications. Medically, his info is dead on.

Yes, his writing is not exceptionally clear but his basic info is pretty simple:

1)You need a minimum CFM to capture fine dust
2)Wood dust is potentially harmful
3)Most hobbiest DC's are too small to do much more than chip collection.

I have a Dylos particle counter and several digital manometers and pitot tubes. His data checks out. Other LJ's that have done the same testing have posted the same. Maybe he's a weird guy and comes across too passionate about dust collection but hey, if I had a bunch of health problems from overstated DC company claims, I'd be pretty passionate too. I'm not sure why this pisses some people off, except perhaps that he tells them what they don't want to hear….that any way you shake it, a HF setup with 4" pipe isn't going to do anything for your lungs.


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## wormil (Nov 19, 2011)

I don't see anger toward Pentz, I see frustration with fanaticism. Like the idea that it's all or nothing with dust collection.


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## Redoak49 (Dec 15, 2012)

I really appreciate the work that Pentz put into his site and providing it free. Who else has made such an effort to provide dust collection information.

If you do not believe it, fine and ignore it. Unfortunately, by the time that you have a problem 20 years from now, it might be too late. Will you be lucky and never have a problem…I hope so.

For me, as I get older, my lungs and such do not work as well and I want to not have a problem. As to wearing a mask, I find them hard to breath thru and is tiring especially if you have one that fits well. I wore respirators for years at my job in a steel mill and these were all OSHA certified and fit checked with a trained person. I was perfectly happy with this as the dust and fumes were very toxic.


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## brtech (May 26, 2010)

Whether you call it anger or frustration, I think a lot of the negative is exactly what Manitario thinks it is: he tells them what they don't want to hear.

I do think he is too strident, but I like passion, and I found it pretty easy to get what I needed from his site. I can look past the passion. I got it, 700 CFM+ to clear fines, and it usually takes >3HP and a big impeller in 6" pipe to get 700 CFM at the tool. YMMV, of course. But it's a decent starting point. When it doubt, get a Dylos. I found his explanation of how to convert from the Dylos readings to μg/m3 clear. I love Mathias' website, and learn a lot from his work. I didn't learn a whole lot from his page on Dylos. It was interesting, but I didn't learn much that I could use.


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## REO (Sep 20, 2012)

Is there a verifiable correlation between WOOD dust and respiratory disease in an otherwise healthy system? Someone mentioned Particulate hazard and others mention small amounts are bad. I have seen results from studies that suggest there is no link between wood dust (unless chemically toxic or already damaged pulminary systems due to smoking chemicals or inorganic mater) and pulmonary diseases. where is the information that says there is accept rumor. I follow several wod turning sites and it is frustrating that the first 100 responses are "Where is your respirator" or "Where is your trend air face shield". I dont hope to flood this thread with opinions. post with reliable test and study results. Specifically wood dust not just dust. "leads to the conclusion" isn't a direct connection."Ive worked with wood for X years and I am or am not ok is not a study ,test or direct correlation either." I am not ok but the jury is still out and the pills my psychiatrist prescribes are too expensive! Occupational safety committees site study's that are inconclusive or suggestive but it is their position to err on the side of caution.


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## Manitario (Jul 4, 2010)

A sampling of articles on wood dust exposure from PubMed, the largest international database of medical research:

COPD and wood dust:
https://www.ncbi.nlm.nih.gov/pubmed/1549828
https://www.ncbi.nlm.nih.gov/pubmed/16749338
https://www.ncbi.nlm.nih.gov/pubmed/6021565
https://www.ncbi.nlm.nih.gov/pubmed/4090537
https://www.ncbi.nlm.nih.gov/pubmed/9470465

Wood Dust and Lung Cancer
https://www.ncbi.nlm.nih.gov/pubmed/26403531
https://www.ncbi.nlm.nih.gov/pubmed/26191795
https://www.ncbi.nlm.nih.gov/pubmed/21856697

Most of these studies controlled for smoking and other occupational exposures so exposure to wood dust was an independent risk factor for COPD and lung cancer.


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## ArtMann (Mar 1, 2016)

You need to keep a couple of things in mind when you read Bill's information. One thing is that his lungs were damaged by something like agent orange that have nothing to do with woodworking. He goes way overboard in my opinion because he could kill himself working in a shop that wouldn't phase most of us. The other thing is he at least used to have a financial interest in a company which manufactures his collector design and components. I'm not saying he is purposely misleading people, but that may have an influence on what he likes and recommends.

If you drill down into the references listed above, you will find that nearly all of the studies were done on people who worked in the woodworking industry for decades. Most of us weekend warriors won't see a year's exposure like that in an entire lifetime.

Having said all that, I still think every woodworker ought to have some kind of system to mitigate dust exposure. On a few occasions, I have found myself coughing and hoarse due to dust inhalation and I don't want to do that again.


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## REO (Sep 20, 2012)

Manitario, the last one is occupational dust not specifically wood dust. others site "furniture factories" and dont exclude finishing chemicals or many of the glues used today both to bond pieces together and in the material itself some of which can cause severe asthma symptoms from contact with the skin without breathing the vapors. others site specific woods known to be toxic. my point is that for most healthy people excluding some of the exotic woods dust wont be a problem. I am not saying those who wear a dust mask or respirator are over reacting it is their choice. To give someone a hard time because they dont and try to back it up as fact when the Closest most studies come is to say that there may be a link is a little off the scale. I have had cancer and may be headed for chemo again soon, on the list of many many contributors in the fine print was wood dust carbon monoxide and tree pollen I have asked three oncologists to explain it to me or show me how wood dust caused cancer. all three did the same search as many here have as I sat in the office. Five years ago they told me that it was not conclusive but it would be better to err on the side of safety. I still dont wear a mask walking down the street or raking leaves. Would it have been better for me if I hadn't worked with wood nope!. if I had worn a dust mask…....for me …....probably not.


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## clin (Sep 3, 2015)

> ...
> I mean look at his page on the Dylos Air Quality Monitor.
> 
> http://billpentz.com/woodworking/cyclone/dylos.cfm
> ...


Regardless of long term health effects, I find that if I keep my shop air clean and make sure to use a respirator, I do not spend the evening coughing.

Even the second link, which more or less concluded that dust isn't so bad, the doctor expert quoted discusses that the mucus in our lungs traps much of this and we cough it up. So yeah, maybe we aren't being hurt, but I prefer not hacking and coughing after spending time in the shop.

In the end, I look at it the way StumpyNumbs put it in a video he did on dust collection and control. If it isn't harmful, but you control dust, the worst thing you do is have a cleaner shop. If in fact it is harmful and you don't do anything, you may suffer.

Also, while Bill makes suggestions for what to do to get the best collection. It isn't an all or nothing thing. I get by with a shop vac (with bad and HEPA filter), Dust Deputy, Jet room filter and respirator. No way am I getting close to getting the fine dust on my table saw using a shop vac. But my system works for me now.

But, maybe some day I'll prefer something that does a better job of collecting at the tool. I'd likely spend less time cleaning the shop.

And I too agree that many simply like to blame the messenger when they don't like the message. But nothing wrong with being skeptical. Though Bill's site always read pretty matter of fact to me.


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## unclearthur (Jul 4, 2013)

I have to say I find the fear based marketing prevalent in woodworking (the Gripper, SawStop, DC) sometimes a bit over the top.

Its not hugely helpful to say 'exposure to fine wood dust can potentially harm your health' and then premise all your advice on an absolute need to remove every bit of dust exiting from your tablesaw. What I don't see is a meaningful evaluation of risks in a real world environment. How big is the risk really in a particular situation? How much are you really mitigating it by spending $5K on a DC system?

Does a Hepa filter actually result in significantly cleaner air in the shop, given all the other sources of dust other than the filter bag? Dust that difference in dust level cause a real difference in the probability of getting sick given that we are breathing in particulates all the time (house, outside, etc) ?

Is having lousy dust collection a bigger risk than crossing the street? Eating a greasy burger every week? Riding a motorcycle? Beats me. I'd be willing to bet that the vast majority of us would add more to their life expectancy by doing 30 minutes of exercise each day than spending $5 K on a DC system.

I'm all for the contributions to DC awareness Penz has made, new safety devices (Sawstop, Gripper), I just hate the preachiness / fear mongering associated with a lot of it.


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## HorizontalMike (Jun 3, 2010)

> "...I have to say I find the fear based marketing prevalent in woodworking (the Gripper, SawStop, DC) sometimes a bit over the top…"
> - unclearthur


Bingo! I think we have a winner (and NOT a wiener)... ;-)


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## wapakfred (Jul 29, 2011)

Like a few others above, I always marvel at the criticism of Bill and his work…whether it's anger, skepticism, or whatever. Look, the man did a hell of a lot of work for his own purposes only…since the info he sought did not exist in the detail he wanted. (Another man found the same thing and did his own work: Bob Flexner.) We owe a great deal of thanks to Pentz for his research. If you don't want to believe him, that's fine. Move on with your life….but all he was doing is sharing what he found.


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## SirTim (Mar 26, 2017)

I like woodworking. Its fun to build furniture and other things that you can't get quality wise in the stores and to be able to say I made it. But unfortunately like other hobbies ( I like photography and scuba diving too) it can be expensive. I know the first time I saw the dust come out of my brand new planer that I had to do something. Me and my Dad invested in a 2hp dust pump. That solved the problem or so we thought. Even with a 4in ducting system, just isn't enough. I have learned this lesson that it is more expensive to by the cheaper system not anticipating spending more to replace it with the one you should have gotten from the start. As an expensive hobby (for me anyway) you save up for new tools and expensive wood and you deal with it. But you get some knowledge from someone who has done all the research (Pentz) and realize he is probably right. But I think for a lot of people the thought of spending the big bucks on dust collection is a waste of money that was not anticipated. The extra costs of something that seemingly hasn't much to do with working with wood never crosses your mind and the hobby gets more expensive. Again you think about the project you want to work on, maybe a new tool and some more wood but not DC. I wear a respirator when I have to but I hate those things. So I cried once money wise with Clearvue and have never looked back. System performance is great, a clean shop and confidence knowing you are getting most of the dust. I hated coming form the shop in the evenings to relax feeling your lungs an nose full of dust.


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## wormil (Nov 19, 2011)

How about backing up the fanaticism with studies that correlate Pentz' it's all or nothing claims with medical data.


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## Redoak49 (Dec 15, 2012)

Everyone approaches woodworking their own way.

Dust collection…breath the dust or not.

Sawstop if you think it is right for you.

Use a blade guard or not.

Use a Gripper or not.

Think that you can always be alert enough to avoid an accident and that is good enough or not.

Believe Pentz or not or use him as a reference or think he is just a fanatic.

Whatever works for you is fine with me. Your safety and how you approach it are really none of my business.


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## Rayne (Mar 9, 2014)

> Everyone approaches woodworking their own way.
> 
> Dust collection…breath the dust or not.
> 
> ...


+1. We all make our own decisions on what's best for us. Take every bit of information we get or get exposed to and make our own informed evaluations and conclusions from it. At the end of the day, you're responsible for what you do. I have seen enough people cough from wood dust or heard enough stories from people with missing fingers to know that I'll do what I can to be safer. I'm currently looking into a Sawstop, even though I have a perfectly fine table saw. It only takes one split-second moment to lose a finger. Grrriper has helped me a lot and now this will be the next step. Is it 100% full-proof? No, of course not; something can always go wrong, but it's the peace of mind I'd like to have for myself while still respecting the tool. Others will be comfortable with what they have and that's perfectly fine. Let's all just be happy we even have this much information available to us.


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## Chashint (Aug 14, 2016)

By now you know dust / chip collection and air filtration are two different animals.
If you have a working furnace blower assembly use it to build an Air filter that doubles as a downdraft table / assembly table / work bench / tool stand / or any other useful structure
Equip it with multiple (3 minimum) filter stages with the first being the cheapest throw away filter at the box store and the last stage being a very good HEPA filter.
Run it 100% of the time while you are working and shop air will be very clean.
See Jay Bates YouTube for his air quality test.
As far as source dust collection goes I would love to have a nice fancy dust collector and if I ever get one I will probably realize how pitiful mine has been for all these years. All I have right now is a very old Delta AP-400 with a aftermarket felt filter bag and hefty drum liner plastic bag for the bottom bag. I put a very simple trash can separator in front of it and move the hose to whatever tool I am using. 
Amazingly enough it works pretty darn good.
I have my concerns about air quality and need to do more to address that, a working furnace blower would be a great beginning to that end in my garage workshop.


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## ArtMann (Mar 1, 2016)

My problem with air filters is that while you are in the shop working, your filter and your lungs are collecting dust at the same time. What I have heard from people who use a Dylos meter is that it takes an hour or more for a commercial filter to remove most of the dust *after* the machines are shut down - in other words, it is too late.


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## clin (Sep 3, 2015)

> My problem with air filters is that while you are in the shop working, your filter and your lungs are collecting dust at the same time. What I have heard from people who use a Dylos meter is that it takes an hour or more for a commercial filter to remove most of the dust *after* the machines are shut down - in other words, it is too late.
> 
> - ArtMann


Your lungs and filter may be collecting dust at the same time, but not at the same rate. An air filter will move something like 1,000 CFM of air, your lungs don't do nearly that much.

As to how long it takes to lower the dust levels, that depends a lot on the size of your shop and the dust level you start at and the level you consider "most of the dust". I have a Dylos meter and a Jet room filter.

But one thing is certain, the filter is going to draw the dust level down orders of magnitude faster than not having any filter at all.

My shop is smallish pretty much equal to a single bay garage (~300 sq ft). I'd say most of the time on high speed it draws it down to quite low levels (about what the inside of my house is at most of the time) in about 15 mins.

While cutting I have the filter on and wear a respirator. I keep the respirator on after I'm done cutting until the Dylos says things are pretty low.

The filter is pretty much on any time I'm in the shop. Just walking around a shop stirs up a surprising amount of dust according to my meter. By the way, that was something Bill Pentz specifically points out. If your shop is covered in fine dust, you don't have to be making fresh cuts to be putting a lot of dust in the air. That is another advantage to a room filter. Less dust settles in the shop and it will help remove it when you kick it up.

If I've been making dust, I usually run the filter (on a timer) for an hour after I leave the shop. Very common for the Dylos to read 0 the next day. And the air actually smells fresh and clean. I've even had people remark on that when they come in the shop.


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## marvinlee (May 28, 2012)

> I m considering building my own dust collector. I found several parts that I scavenged and one of them is a HVAC furnace blower from a neighbor who replaced their HVAC system. As I understand it, the RPMs are too low to create enough static pressure, so I will have to replace the motor with a higher speed AC motor. I have quite a collection of 1/2 HP to 1 HP motors I can use. The squirrel cage will have to go, leaving me with only the housing which may work for housing the impeller and motor.
> 
> I ve been reading all kinds of resources online and was very excited about this project until I stumbled upon Bill Pentz s site. He is supposedly an expert on dust collectors and has extensive information on how to build one. Unfortunately, he really scares the crap out of me for not having a proper one and then scares the crap out of me if I don t build it according to his specifications, which costs as much or more than an decent dust collector.
> 
> ...


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