CFM Numbers - More Confused Then Ever

[Rob Luter]

Rob what disturbs me is that Mr. Pentz is quoting numbers from OSHA and when I talked to them they had no idea what I was referring to. In other words they did not provide the data. The same for ACGIH. And then Euro Medical which I can't find any reference to. These numbers are being presented as coming from a government industry and an engineering think tank. I feel this is basic misinformation. Where are the root sources for this information? Where can I find data that supports this so I know I made the right decision? Do we accept these numbers as blind faith?

I'm not sure who you talked to at OSHA, but as large a bureaucracy as they are, it's not surprising that they didn't have a clue. In my dealings with them in the past (defending their inquisitions) they did not impress. Their typical MO was to investigate wild claims by disgruntled employees, pass judgement using half the facts and less than half of their wits, initiate punitive action, and fold up like a lawn chair when our HSE people read them their own rules chapter and verse. I'm sure not all in the organization are that way, but I'm just saying.....

I'd stick with the Industrial Ventilation Guide from ACGIH. Use their work as a starting point.

[Carroll Courtney]

Brent,you being a School Administrator why not take a tour of your high school wood shop classes and see how their's are set up.Maybe talk to the shop teacher about the dust collection.

[harry strasil]

Pardon my intrusion, but someone did mention velocity as a key factor in dust/chip removal, but no one has mentioned the negative aspects of using a large CFM machine and the relationship of throttling the intake down with multiple elbows and long runs due to friction loss in the system or the necessity of keeping the exhaust cleaned. Most if not all of the basic suction producing machines are of the impeller type and throttling (blocking off or reducing) the intakes and exhaust too much will make the fan run in a vacum or greatly reduce the velocity of the whole system.

Just something to think about. FWIW

[Dave MacArthur]

I am not at all surprised that Brent had trouble verifying sources and numbers by calling the listed agencies. These agencies are enormous beauracracies! The chance of working your way through the gov't employees to a person who has any REAL KNOWLEDGE of the area is unlikely--particularly in that everyone along the way tends to stand on some paper published by the agency, claim unfounded expertise, and pretend they are the final answer-guy beyond which you need not go.

Now, even if you DO reach a gov't employee who is knowledgable in Dust Collection, what is the chance that they are truly read-up and expert in home hobby shop collection, and ready to quote you the info from recent objective testing of machines like yours? NONE. In most cases they will refer to internal studies which are every bit as nebulous in their setup/control/methodology/applicability, but they will not divulge that info to you. Trusting information from OSHA or similar gov't beauracracies as the Source of Holy Rightness is questionable. They have neither the inclination, motivation, or funding to research setups fully applicable to you.

Having been the Chief of Safety for a USAF base with a full team of ground and engineering safety workers, with a mandate to observe and comply with OSHA guidance and indeed pass inspections, I have had numerous chances to track down questionable data with them. In virtually every case where data was questioned such as when engineering a system not perfectly in line with published assumptions, it was an extremely onerous and long process finding a truly qualified expert and getting an objective look by him, generally taking several weeks. I would be extremely surprised and impressed if a person attempting to work through that red-tape without previous experience in dealing with them were able to get a truly comprehensive answer in a day.

If OSHA were forced to list the EXACT name and personal info of the engineer responsible for their position and charts, how do you think he'd stand up against scrutiny? How much time do you think he would have spent researching wood hobby shops, truly? It's easy to forget that there really is no "OSHA Position", merely a position put forth by a generally small number of engineers and adopted.

Just some input to help you put your inability to quickly verify data in perspective. I for one, having read Mr. Pentz' site from cover to cover, find his work and analysis selfless and comprehensive. I found numerous justifications in his writing for boosted CFM numbers which seemed reasonable assumptions or conservative estimates to me, given that one only reads that much info if one is concerned with your own health. While I have not attempted to verify his source data, it all seemed order-of-magnitude reasonable enough in comparison to other sources.

Good luck to you, I salute your efforts and research--more discussion on this area can only help--but hope you'll be more ready to give Mr. Pentz the benefit of the doubt.

[Brent Simons]

I think we are all on the same page as far as wanting to reduce dust exposure where possible in the wood shop, and certainly Mr. Pentz has added value here. How much dust is OK is another debate that will probably never end. I wear a $20 dust mask most of the time in my shop anyway. I do think including references and tests would go a long way in helping his cause and would lend a lot of crediblilty to him if he put the supporting information on his website. I E-mailed Mr. Pentz about these things.

Brent

[Hank Phillips]

I think we are all on the same page as far as wanting to reduce dust exposure where possible in the wood shop, and certainly Mr. Pentz has added value here. How much dust is OK is another debate that will probably never end. I wear a $20 dust mask most of the time in my shop anyway. I do think including references and tests would go a long way in helping his cause and would lend a lot of crediblilty to him if he put the supporting information on his website. I E-mailed Mr. Pentz about these things.

Brent

I've been going through a similar learning curve in researching for a DC for my shop. Perhaps I'm overly concerned with good dust collection as others here have admitted to be.
I read through Mr. Pentz site too, as well as a bunch of other places, and some of the info on his site doesn't add up... some info is just incorrect. There's what seems like a lot of information that isn't backed up.

For Example, Mr. Pentz says in his site that the European wood dust permissible standard is 50 times less than the US OSHA.
From Pentz site, “The European community reduced their maximum exposure limits over an eight hour day to the medically recommended 0.1 milligram per cubic meter of air. That is fifty times tighter than current OSHA standards.”

Well, the references I've found (easy to find on the web) state that as of March of 2006 the EU standards are the same as the US, at 5 mg per cubic meter of air, not 50 times lower. Maybe it needs to be lower, but that’s not the point here.

Find site at http://annhyg.oxfordjournals.org/cgi/content/full/50/6/549Occupational Exposure to Inhalable Wood Dust in the Member States of the European Union. “The EU has set an exposure limit for invaluable hardwood dust (5 mg m–3 as an 8-h time-weighted average)” Other reference sites: [FONT='Arial','sans-serif']www.arbejdsmiljoforskning.dk/upload/WD-abstract-Timo_Kauppinen.pdf[/FONT]

That's just one example... he's obviously put a lot of time into the subject, but I for one can't take his word for gospel, especially after seeing the conflicting/incorrect info he has on his site. I guess I have a "where there's smoke there's fire" attitude, and like anything else, you have to do your own homework and get a second or third opinion and decide what you think is right.