Is Bill Pentz dust collector safety exaggerated?

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Forum topic by RichardDePetris posted 06-10-2015 06:06 AM 2409 views 0 times favorited 41 replies Add to Favorites Watch
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44 posts in 1105 days

06-10-2015 06:06 AM

Topic tags/keywords: question resource

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 ( 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.

41 replies so far

View Rob's profile


704 posts in 2490 days

#1 posted 06-10-2015 07:01 AM

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.

-- Ask an expert or be the expert -

View djg's profile


159 posts in 1582 days

#2 posted 06-10-2015 08:33 AM

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

View hhhopks's profile


645 posts in 1797 days

#3 posted 06-10-2015 10:00 AM

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.

-- I'll be a woodworker when I grow up. HHHOPKS

View Pezking7p's profile


3097 posts in 1071 days

#4 posted 06-10-2015 10:13 AM

The thermite thing is exaggerated.

-- -Dan

View Fred Hargis's profile

Fred Hargis

3841 posts in 1913 days

#5 posted 06-10-2015 11:41 AM

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.

-- Our village hasn't lost it's idiot, he was elected to congress.

View English's profile


512 posts in 897 days

#6 posted 06-10-2015 11:57 AM

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.

-- John, Suffolk Virgina

View hotbyte's profile


825 posts in 2395 days

#7 posted 06-10-2015 12:03 PM

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.

View rwe2156's profile


2114 posts in 900 days

#8 posted 06-10-2015 12:11 PM

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.

-- Everything is a prototype thats why its one of a kind!!

View Crank50's profile


170 posts in 996 days

#9 posted 06-10-2015 12:19 PM

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.

View timbertailor's profile


1591 posts in 844 days

#10 posted 06-10-2015 12:22 PM

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

-- Brad, Texas,

View ksSlim's profile


1203 posts in 2309 days

#11 posted 06-10-2015 12:32 PM

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.

-- Sawdust and shavings are therapeutic

View TheWoodenOyster's profile


1275 posts in 1355 days

#12 posted 06-10-2015 12:33 PM

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.

-- The Wood Is Your Oyster

View Rob's profile


704 posts in 2490 days

#13 posted 06-10-2015 01:43 PM

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.

-- Ask an expert or be the expert -

View CharlesA's profile


2973 posts in 1217 days

#14 posted 06-10-2015 02:38 PM

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.

-- "Man is the only animal which devours his own, for I can apply no milder term to the general prey of the rich on the poor." ~Thomas Jefferson

View AZWoody's profile


680 posts in 644 days

#15 posted 06-10-2015 02:44 PM

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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