CFM Numbers - More Confused Then Ever

[Jim Becker]

Could someone advise of Oneida's website address as they are referenced several times here.

http://www.oneida-air.com

[Chuck Lenz]

Brent I think your way over thinking this. I would go with Bill Pentz's advise or Oneida's. Dust collection is a pretty tough task, most dust collectors are basically chip collectors because DC bags don't capture the really fine stuff that is hazzardous to you. Cartridge filters will do a better job, but geting everything at the source such as a tablesaw, sander, mitersaw, etc. is just about impossible. For this I recommend a air filtration unit and a good quality dust mask. If your a one man shop running one tool at a time a 1 1/2 hp - 2 hp dust collector should be plenty for you if you duct it correctly with smooth walled hose or ducting weather it be metal or PVC. I won't say that I know it all, but this is the best way I know how to explain it from my experience. For instance it may take more CFM to get the same amount of dust from one brand or model of tablesaw than the other brand or model. So in saying that tablesaws in general need 650 CFM of air to collect dust effeciently is really just purely a guess or round about number or even a starting point. There are too many different types of tablesaws to say that they all need the same CFM.

[daniel lane]

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?

If you ask my wife, she will tell you that I am a stickler for references. One of my greatest pet peeves is people that present statistics or hard numbers as fact without giving a source for those numbers. It sounds like you have a similar problem here, albeit with a reference that doesn't match up, rather than with no reference. Everything I've seen and heard about Bill would belie the thought that he is purposely presenting false numbers. In your shoes, I would contact him directly and ask, "Hey, Bill, I was looking for more detail regarding the numbers on your website and not only can I not find them, but agency reps don't know where they came from either. Do you have a reference so I can go read more?"

I once spent a lot of time doing calculations for air emissions permitting for a chemical company. I had a bad photocopy of a portion of an EPA book with sample calculations so I called the EPA and asked where I could buy the book. It took me over 30 minutes with an EPA librarian to track down that such a book even existed. The information was real and valid, but was very old. At first glance, the agency had no idea where the information I was holding had come from.

Just because a government agency doesn't know where numbers came from doesn't mean that they themselves did not report those numbers. Just because somebody is presenting information that you cannot independently verify doesn't mean there is a deliberate misinformation campaign. Give Bill a chance - call (or email) him and ask. And at the end of it all, if you decide that you don't trust one set of numbers over another, then you can deny the first set your blind faith and feel confident in your decision to use the other.


daniel

[Art Mann]

I don't know if I agree with that Art, but certainly exposure to the hazardous particles is lower (not necessarily risk).

Here is my rationale. Let me draw an analogy with cigarette smoking. Nobody in his right mind will claim that a teenager trying a single cigarette for the first time will compromise his health in any meaningful way. On the other hand, very few people believe that 30 years of smoking cigarettes will have no effect on the health of an individual. There is a mathematical relationship between the degree of exposure over time and the degree of health risks that result. This is not a hypothesis, but has been proven by countless studies. Although I can't prove it, I have no reason to believe wood dust exposure works any differently. There is certainly no data to contradict this idea.

The studies I have seen show somewhere between zero and a very tiny increase in the risk of respiratory illness as a result of continuous wood dust exposure at the OSHA recommended concentration over many years in the workplace. I am striving to achieve the same standard as the industry requirements in my home shop. My overall exposure will be less by an order of magnitude. I figure that if I even come close to OSHA standards, my health risk will be pretty much zero.

Mr. Pentz would not, of course, agree with me on this position.

[Wilbur Pan]

Here is my rationale. Let me draw an analogy with cigarette smoking. Nobody in his right mind will claim that a teenager trying a single cigarette for the first time will compromise his health in any meaningful way. On the other hand, very few people believe that 30 years of smoking cigarettes will have no effect on the health of an individual. There is a mathematical relationship between the degree of exposure over time and the degree of health risks that result. This is not a hypothesis, but has been proven by countless studies. Although I can't prove it, I have no reason to believe wood dust exposure works any differently. There is certainly no data to contradict this idea.

Art, the mathematical relationship you are referring to is a dose response curve. What the dose response curve says is that if you take 100 woodworkers and expose them to a low level of dust, a small percentage of them will develop debilitating lung disease. Increase the dust exposure, and more will get debilitating lung disease.

This does not mean that for an individual, that more dust means more lung disease. Although the small percentage of woodworkers in the low dust group get lung disease, the magnitude of that lung disease can be very severe.

In other words, take woodworkers as a group, and you can use percentages. Take an individual woodworker, and debilitating lung disease turns into an either/or condition.

Furthermore, the mechanisms of wood dust-induced lung disease make this not analogous to your cigarette/lung disease example. Many of the disease processes that stem from wood dust involve inflammatory responses in the lungs, and are based on the fact that you can have a very large inflammatory response from a very small exposure. This data certainly contradicts your assertion.

By the way, a single puff on a cigarette can cause a severe, life threatening asthma attack.

In any case, none of this changes the fact that an single sawing or sanding operation can generate dust that exceeds current guidelines.

[Steven Wilson]

Brent,

It doesn't surprise me that you aren't able to find much scientific data posted on the Internet. The nature of the beast precludes it. To properly research peer reviewed, scientific journals or the output of standards groups you need to subscribe and that's rather expensive. University libraries are a great source for access to this information. If you are interested in Mr. Pentz's sources I suggest that you contact him for that information.

As for your concern about non-rounded up numbers, many of those were probably listed in metric units originally and then converted by Mr. Pentz into the CFM units were comfortable with (i.e. m3/h is used for air flow rates ).

I've experienced some negative respiratory effects of woodworking with older style woodworking machines and chip collectors. I sold my American designed WW machinery and picked up a European combination machine as well as improve my sanding capabilites by using Festool products.

The dust collection capabilities on the saw/shaper portion of my combination machine are superior to what is typically found on American designed light industrial equipment (i.e. Powermatic, Delta, etc). The collection capabilities on the jointer/planer is better but could be improved (they also produce more chips and less dust than a saw/shaper). I'm not convinced that 800CFM at the tool hood is necessary (but it is definately a good idea) but what we have in our typical machinery is inadequate. Since my machine is designed and sold in Europe I expect that it needs to meet their tougher standards. As an example, the following are the minimum airflow requirements listed for the various functions on my machine (converted to CFM). When designing my DC system I tried to exceed those requirements.

Machine Airflow(CFM)
Shaper 441 upper hood, 441 cabinet
Saw 100 upper hood, 441 cabinet
Jointer 441
Planer 441
Mortiser 441

all airflow at 3937 ft/m velocity

[Mike Spanbauer]

I agree with striving for the best solution you can afford / deem reasonable Art no argument there at all from me.

It's why I have a system that pulls 1200 CFM @ 6" SP maintaining 3922 FPM. It's might be overkill, but the only weakness is the hoods @ the tools and not the system / piping / DC itself.

I've sensitive lungs and my 6 year old has asthma. I personally have no issue over-investing in the DC given that I want him to be able to work with me and the cost of an issue or complications for him resulting from dust... Let's just say that's not something I want to consider

mike

[Art Mann]

Brent,

It doesn't surprise me that you aren't able to find much scientific data posted on the Internet. The nature of the beast precludes it. To properly research peer reviewed, scientific journals or the output of standards groups you need to subscribe and that's rather expensive. University libraries are a great source for access to this information. If you are interested in Mr. Pentz's sources I suggest that you contact him for that information.

That is not what I was saying at all. On the contrary, you can find all kinds of studies on the internet having to do with the health risks of wood dust exposure, a few of which were referred to me by Bill Pentz. In some cases, all that is available is a summary of the findings, but that is good enough for me. What I am saying is that these studies generally do not show a very large health risk to people working in an environment where OSHA standards are adhered to. A few of the studies I saw showed no adverse affects and several others were inconclusive.

If you keep digging, you can find position papers written by various government agency employees that claim there is some risk, but these are nothing more than personal opinions.

Incidentally, the flow rates you list for various woodworking machines would be considered inadequate by Bill Pentz.

[keith ouellette]

I ran into the same kind of problem whe I was setting up my shop. I talked to several people and told them the size of my shop and what I wanted to do and recieved different answers from everyone. I finally gave up and just bought a 1200cfm machine and hoped for the best. I used 4" waiste line pvc. It saved a lot of money. I didn't ground it though I'm told I should. It runs along the cieling and down the walls to a gate at each machine. The cieling is ten feet high and the collector is out of the shop in its own room as high as the cieling. My eight inch jointer is fifteen feet away and all the chips pull through very well. The table saw is the same distance but does let some fine dust out but that may be do to the design of the cabinet. A two inch hose streched twenty feet to my work bench will pull most of the dust from my router in most opperations. There is always fine dust on the floor though but not too much. I hope this gives you a little help in planning.

[Chris Parks]

I think the simplest thing to resolve this to ignore all of Bill's advice, work in the shop cutting wood for 8 hours a day for 1 year and let us know what happens. We need a real live volunteer and you sound just like the person willing to do it. You are questioning the efforts of a pioneer and no one who is a pioneer in health related issues such as this gets away without being denigrated by every company, agency and person who they disagree with, witness the cigarette companies attempts to squash any criticism of them in times past. Don't read his numbers, read his research and conclusions and then decide if his numbers are worth the consideration. Why would you question findings that at the least can't harm you and should, even at the most cursory glance benefit you? No wonder Bill feels the way he does.

To Bill, keep up the good work, you are a pioneer and pioneers get the stuffing kicked out of them by people and companies whose boat you rock.

[Art Mann]

I think the simplest thing to resolve this to ignore all of Bill's advice, work in the shop cutting wood for 8 hours a day for 1 year and let us know what happens. We need a real live volunteer and you sound just like the person willing to do it. You are questioning the efforts of a pioneer and no one who is a pioneer in health related issues such as this gets away without being denigrated by every company, agency and person who they disagree with, witness the cigarette companies attempts to squash any criticism of them in times past. Don't read his numbers, read his research and conclusions and then decide if his numbers are worth the consideration. Why would you question findings that at the least can't harm you and should, even at the most cursory glance benefit you? No wonder Bill feels the way he does.

To Bill, keep up the good work, you are a pioneer and pioneers get the stuffing kicked out of them by people and companies whose boat you rock.

You don't need volunteers. There are thousands of small cabinet shops across the US where owners have been doing exactly that for decades. The answer to your question of what will happen in most cases is "nothing". They are not all dead. I don't think it is a wise thing to do, but that is the reality.

I don't see a problem with someone trying to verify controversial claims made by another person who represents himself as an expert. His website has some very good information on designing dust control systems. However, it seems a little long on opinion and short on evidence when it comes to health risks.

[Greg Dykes]

Brent, I believe I get your point and I too agree there is to much confusion. I admire your research into the facts that have been posted by Mr. Pentz. Like you, I like to take the advice from two or three and then decide what is right.

I have receieved certification through the Florida State Fire College as a fire service instructor. I am a U.S. Coast Guard approved instructor, EMT and certified by the American Heart Assoc. & Red Cross as a emergency health care instructor. With all that being said, I have spent by fair share of days in classrooms listening to so called experts and believing everything they say until you experience it for real. More times than I would like to remember these so called experts have made up facts. I myself make sure I have material to back up everything I teach a student to cover by butt in case I am ever sued in cival court.

In this particular instance I referenced Bill's site before buying a DC. I was scared to death to even walk into my shop/garage based on the facts that were presented. I imediately set out to buy the biggest badest DC ever made because I thought I need all this CFM to run my tools.

Before I built an addition on the house to store one of these monsters or had to cash in my 401K I went to a local ole timers shop here in town. Like me, he runs one tool at a time in his garage and was using a 1 1/2HP grizzly w/ 1 micron filter. His shop was free of even small particals of dust (the kind that can be seen or felt). Based on this I bought a 2HP unit from HF and upgraded with a filter kit. I am extremly happy. Oh yeah, one other thing to mention. I had to retire from the fire service because of a respritory illness. House hold dust can make me double over coughing. I have not had any problems in the shop (I do wear a disposable mask).

I think Brent was just trying to point out that most of use (me included) were going to, or did base our purchase of a DC on what we read on Bill's site.

I have posted many times on this site seeking advice. I want to thank everyone that responded. However, in most every case I received from 2-8 different answers. What this made me understand is that I needed to look to a source that was an authority on the subject with published data that I could reference. If the responses to my question had a majority responding with the same answer I would not have looked any further.

Time to take my prozac and watch Andy Griffin.....

[Fred Craven]

This whole discussion on confusion over numbers points out an interesting evolution in work place safety...or at least in dust collection.

Once upon a time people didn't care. Dust collection was really chip collection and the motivation was to make it easier to clean up--not for ones health. Even cyclones seemed to only offer an advantage in that they reduced the need for having to clean a filter!

I don't know where Bill Pentz got his original numbers but he has become the seminal source for dust collection information in woodworking. In the woodworking community he pioneered the concept that dust is bad for your health. Wether his numbers are high or low, Bill's research, conclusions, and published findings are the reference standard most of us use.

This single individual can't be avoided by any company who markets a dust extraction system (especially cyclones) eventually someone will ask, "how does this compare to what Bill Pentz says?"

It appears as if we are moving to the next level of dust collection studies. Call it "academic research and criticism." If I were a mechanical engineering student working on my master's or doctorate, I think an thesis or dissertation on dust collection in woodworking environments would be quite interesting. And any such research would have to cite Bill Pentz.

Thanks Bill.

[Eric Gustafson]

And any such research would have to cite Bill Pentz.
Thanks Bill.

I could not agree more. Let us also consider how useful his data and website are on dust collection for us average Joes (and Jills .) There is nothing on the internet more complete or exhaustive on the subjeuct. Bill could have published this and sold the book and we would have all had a good deal, but the information is free. Every nuance to be considered in a dust collection system is there.

BTW (gloat), Just bought the CV-1800 from the clearvue guys yesterday.

[Brent Simons]

I am still looking for options on dust collectors. Thanks to all for advice and opinions, but I am still more confused than ever. Can't make up my mind. Anyone notice the new Oneida site? It has a lot more on it. It has a very friendly E-mail dialog between Bill Pentz and Oneida’s president. Based on some unsolicited E-mail I got from Bill P. this was very surprising. What’s the story here?