CFM Numbers - More Confused Then Ever

[Brent Simons]

I am in the process of setting up my duct system for my shop. In my research on a Google search I found a chart of requirements for Woodworking Operations on Bill Pentz’s cyclone site. Oddly I found that these numbers were much higher than any other agency recommendation. After an exhaustive search of the OSHA site I found two links: One on woodworking hazards:

http://www.osha.gov/Publications/woodworking_hazards/osha3157.html (http://www.osha.gov/Publications/woodworking_hazards/osha3157.html)

and the other on dust collection:

http://www.osha.gov/SLTC/silicacrystalline/dust/chapter_3.html (http://www.osha.gov/SLTC/silicacrystalline/dust/chapter_3.html).

All of this is excellent information on dust collection, but I could not find any CFM requirements for WW tools published by OSHA as per Mr. Pentz’s chart. Here is a link to the chart…

http://billpentz.com/woodworking/cyclone/DC4Dummies.cfm (http://billpentz.com/woodworking/cyclone/DC4Dummies.cfm)

So then I decided to call OSHA. After speaking to several people they finally said they don’t publish CFM values for WW shops and the information on Mr. Pentz’s chart is wrong. They recommended that I contact ACGIH for the information that I needed and pick up a copy of the “Industrial Ventilation Guide” printed by the ACGIH which is the American Conference of Gov’t Industrial Hygienists. Their website is www.acgih.org (http://www.acgih.org/). (http://www.acgih.org/)

ACGIH is a committee comprised of academics and engineers that publish the “Industrial Ventilation Guide” which includes how to set up duct systems for central dust collection systems. I purchased the book (very expensive) and after considerable research I didn’t find any of Mr. Pentz’s CFM requirements anything close to the values ACGIH publishes, although he states they are, ”updated from ACGIH.” The person I spoke to at ACGIH said that these machine CFM values for woodworking tools were developed by ACGIH engineers and industrial hygienists over a period of 50 years and are the current benchmark standard for industries. Mr. Pentz’s recommendations are in most cases approximately double the ACGIH recommendations. I am now totally confused.

Searching for the last column on Mr. Pentz’s chart titled “Medical (Euro) recommended Exhaust CFM” I ran into the same problem. I Googled extensively but could not come up with any information on Medical (EURO) exhaust CFM for WW tools that was anything like Mr. Pentz’s chart.

As a last resort I called the UK Safety Executive. This is roughly the equivalent of OSHA. A really friendly chap said that he never heard of any Euro Medical Organization that recommends CFM exhaust requirements for WW shops. For example Mr. Pentz’s Chart shows 889 CFM for a 12” radial arm saw. The ACGIH manual says 500 CFM. Mr Pentz recommends 889 CFM for this tool nearly twice the other recommendations. I am left wondering where Mr. Pentz gets his data from.

I took the liberty of posting ACGIH CFM diagrams and also Mr. Pentz’s chart. So far none of it has checked out with the agencies he has purported to have copied information from. Also, all agency CFM numbers I found are all rounded; for example 350 or 430 CFM. Based on the odd numbers on Mr. Pentz’s chart for example his numbers are 889 or 981 CFM. No agency that I could find lists numbers like this. I can’t find any information anywhere that supports his data or the reprinting of Agency data. Has anyone else researched this? Has anyone run into this? Where does Mr. Pentz get this information for his chart? I have to say that this is very disappointing. I trusted his info for my DC system and design. Can anyone help.

[Dave Anderson NH]

Many dust collection threads on SMC have a habit of degenerating into name calling and personal attacks. They also generate bashing of equipment suppliers products, often without supporting evidence.

Other moderators and I will be watching this thread closely. Posts which violate the SMC Terms of Service will be edited or deleted immediately.

Let's keep the thread on topic and the tone friendly and informative. Generate light, not heat.

Dave Anderson NH

[Eric Gustafson]

I have not read everything on Bill's website, but your diligence to detail is commendable. I do not know the guy, but I appreciate the knowledge he has shown.

My spin on what Bill has written is that the man is obviously passionate about dust collection. Rather than trust the numbers it seems he has done some objective research. Regardless, when it comes to CFM requirements, it seems that more cannot but help, rather than hurt. Excepting one's wallet of course. :eek:

Personally, I would rather be safer than sorry. I am in the market for a dust collection system right now and will use Bill's information as well as other sources before I make my final decision.

[Alan Schwabacher]

Have you tried sending this question directly to Pentz?

[Ed Labadie]

I agree with Eric, your diligence to detail is commendable.

It might be a better start if you gave some basic information about your planned dust collection sytem and shop setup, then others can relate their experiences, both good and bad.
I referenced Bill's information when I did my system, it was very helpfull. The people at Oneida were also helpfull and patient with me. :o
Eventually you must start on the system, it can be a somewhat frightening task, but don't be intimidated, go slow and ask lots of questions as you move along.

Ed

[Dick Sylvan]

My spin on what Bill has written is that the man is obviously passionate about dust collection. Rather than trust the numbers it seems he has done some objective research. Regardless, when it comes to CFM requirements, it seems that more cannot but help, rather than hurt. Excepting one's wallet of course. :eek:

Personally, I would rather be safer than sorry. I am in the market for a dust collection system right now and will use Bill's information as well as other sources before I make my final decision.

I couldn't agree more. If you want to be conservative, use Bill's numbers. If you want to be less so, use the other set which I would doubt are really "tailored" to home woodworkers. Also, a major variable is the type of collection "at the tool" that you have. For example, my new Hammer has a dust collection shroud around the saw blade which directs the dust into the collection system. My old Jet cabinet saw (which I thought was a fine saw) merely had a ramp at the bottom which I thought was minimally effective for dust collection. So would I need a more powerful DC for the Jet over the Hammer? Probably, but I am still going with what I consider overkill for the size of my shop, i.e., a Clear Vue.

[Rob Luter]

I feel your pain Brent. I spent a number of years as a ventilation Engineer. The Industrial Ventilation Guide is a great resource. It presents a good framework to work within, with all else equal. The kicker is: all else is rarely equal.

The data presented in the IVG is a good place to start. In my experience, the conveyance of particulates (sawdust and chips) in an airstream is a function of not only air volume (CFM), but also air speed (duct velocity). You can be moving a ton of air but if it's moving too slow it won't have sufficient velocity to keep the particulates "moving down the highway". The velocity across the face of the hood or other duct termination where the dust is collected is important too. This is often referred to as "Capture Velocity". If the air isn't moving at a fairly brisk pace it won't suck the chips in unless they're directed right to the duct termination. If you can direct the chips straight to the duct using a shroud or other mechanical means, capture velocity is less important.

I took a quick look at the Bill Pentz site, and he does a good job of presenting these and other related principles. If the only issue you have with his information is CFM recommendations then I think you're in pretty good shape. Agency publications will generally cite minimum requirements for generic applications. Mr. Pentz appears to have chosen to use data based on field experience with specific applications. His sections on Airflow and Resistance spell this out pretty clearly.

If you set up your DC system and find yourself low on air, you're pretty much screwed. On the other hand, if you find you have excess airflow capacity it can be dealt with. It's a similar problem to having saw blades that are too sharp, fences that are too straight, Benches that are too flat, and joinery that fits too well.

My $0.02 worth ($0.015 after taxes)

[Ron Williams]

I do not know how complex your shop is but I simply used the info available on Oneida's web site to design my system and it works great. I have 8 machines that are hooked to this system. I worried about this alot before I jumped in and simply did it Good luck

[Art Mann]

Mr. Pentz has suffered some pretty serious respiratory problems that he attributes to wood dust. His opinions on what is and isn't safe are strongly influenced by that experience. One would do well to keep that information in mind when evaluating his recommendations.

Another thing to keep in mind is that the OSHA standards are for employees in the wood processing industry who are exposed to dust on a continuous daily basis. If you are a hobbiest, your relative risk is much lower than that of a professional woodworker.

[David Giles]

1. More airflow gives better dust capture.
2. More airflow requires bigger, more expensive ducts and more power consumption.
3. Life's full of tradeoffs. The sweet spot differs from person to person.

[Brent Simons]

I took a quick look at the Bill Pentz site, and he does a good job of presenting these and other related principles. If the only issue you have with his information is CFM recommendations then I think you're in pretty good shape. Agency publications will generally cite minimum requirements for generic applications. Mr. Pentz appears to have chosen to use data based on field experience with specific applications. His sections on Airflow and Resistance spell this out pretty clearly.

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?

[Paul Hendrickson]

I'm a chemist with many years of experience with gov't agencies publishing data about what level is safe and what is not. I can tell you that some are silly in their unreasonableness, and others have me scared to death to think what is "legal and aceptable".

Having said that, respiratory problems are nothing to be taken lightly. Remember, it's not the particles you can see that hurt you. There is a reason why there is such fanaticism with regards to asbestos. It is not to be taken lightly.

If there is a decision to be made, I choose to err on the side of caution. Don't know Bill, but I appreciate his passion. His willingness to freely share information, rather than charge for it speaks to his character. You can learn all you want from him and build your own system and he won't make a penny off of you. That speaks volumes to me.

Finally, if you really want to know about Bill's numbers, why not ask him?

[Wilbur Pan]

This may not address all the data that you are looking for, but I posted a list of references to peer reviewed journal articles relating to the health risks of dust (http://www.sawmillcreek.org/showpost.php?p=454754&postcount=98) a while ago. One of those articles cites the ACGIH guideline for total dust exposure is 1.0 mg/m3 for an 8 hour period.

One of the articles found that a single sawing or sanding operation alone could expose a person to more fine dust alone than the amount of total dust he/she should be exposed to for an 8 hour shift. Couple this with the fact that most home shops are not as well ventilated as industry environments, and the assertion that hobbiest shops must be safer simply doesn't hold.

[BOB OLINGER]

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

Thanks,

Bob O.

[Mike Spanbauer]

If you are a hobbiest, your relative risk is much lower than that of a professional woodworker.

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

OP:
Some links for reference and the real authorities on dust regulation:
http://www.osha.gov/SLTC/healthguidelines/wooddustallsoftandhardwoodsexceptwesternredcedar/index.html (http://www.osha.gov/SLTC/healthguidelines/wooddustallsoftandhardwoodsexceptwesternredcedar/index.html)
http://www.osha.gov/SLTC/healthguidelines/wooddustallsoftandhardwoodsexceptwesternredcedar/recognition.html#exposuresources (http://www.osha.gov/SLTC/healthguidelines/wooddustallsoftandhardwoodsexceptwesternredcedar/recognition.html#exposuresources)

About 1/3 way down the second link you'll find the measure that the various agencies use for permissable particle levels in industrial environments.

I did find the ACGIH materials linked, but they are fee based and require a membership or login. (ACGIH [1994]. 1994-1995 Threshold limit values for chemical substances and physical agents and biological exposure indices. Cincinnati, OH: American Conference of Governmental Industrial Hygienists)

The challenge as Art has pointed out though is that all regulations are for industry and not for hobby / home.

The suggested guidelines / CFM requirements for each tool that Bill suggests are just that, guidelines. They can't be hard and fast as each tool has a unique hood design, flow through, and chip / particle production measure. A contractors saw is a much worse dust offender than a cabinet saw by virtue of the open design and lack of integral DC port (only an example).

The issue of course, and the reason why this is such a volatile topic is that it is VERY difficult to determine exactly how dangerous wood dust is, in what volume, and what sensitivity level each of us has.

You know, it's ironic that such emotion gets raised over DC's. People want a warm fuzzy that they have good dust collection and they want to hear that there is no risk in wood working when they meet a certain level of dust collection equipment... The reality is that there IS inherent risk in woodworking. Dust, machinery, and Darwinism :) A moments carelessness can result in the loss of a finger or worse, but dust inhalation is a much, much slower and insidious affliction.

The ONLY way that anyone could state with absolute certainty there is no harm from wood dust is to stop woodworking all together. Of course, that's not acceptable to many here (myself included :)) so we attempt to protect ourselves as best as we can. The only way to do that is by doing homework and taking measures to preserve our health.

Bill has invested a great deal of time and effort into raising the visibility / need for adequate dust collection in the home shop and for that I think that many (including those who don't support bill) will credit him with a good deed. Bill's efforts increased every dust collection vendors sales, and improved the air quality in many of our shops in so doing.

If you're looking for specific measures of CFM required at each machine, the only hard and fast figures would have to come from each machine vendor. Many do provide guidelines, but not necessarily specific machine figures. Consider the PM2000 with its very nice internal shroud around the blade vs. my PM66. I am certain that the PM2000 is a much more effective dust collector than my PM66... 600, 800, 1000? I can't tell you and I am not certain that Powermatic even did this testing.

Whatever you're comfy with is what you need to design for. Guidelines only get you so far :)

mike

[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:rolleyes: .) 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.:D

[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?

[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/50/6/549 (https://exchange.oneida-air.com/exchweb/bin/redir.asp?URL=http://annhyg.oxfordjournals.org/cgi/content/full/50/6/549) Occupational 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: www.arbejdsmiljoforskning.dk/upload/WD-abstract-Timo_Kauppinen.pdf (http://www.arbejdsmiljoforskning.dk/upload/WD-abstract-Timo_Kauppinen.pdf)

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.