Dust Piping Reality

[Alan Schaffter]

Let me stir the pot with a few random questions

What do the OSHA recommended machine CFM numbers mean? What effect does achieving only 3/4, 1/2, 1/4, etc. of the recommended CFM have on large and small dust particle density at the machine? What are the OSHA recommended maximum small and large particle densities? What are the maximum and minimum exposure times for both? How were they determined and what do they mean? What does it mean if you exceed either? Is there a documented, quantitative direct correlation between dust exposure (both density and time) and adverse health effects or is most of it anecdotal?

When using a Dylos, aren't readings taken where the worker is standing (Dylos hung around the neck?) at the time he is using the machine more important than readings taken 10, 15, 20 min. later when the user is sucking much lower (many times lower?) dust densities? What kind of dust density is the user exposing himself to when sawing MDF on a tablesaw that is not equipped with an over-blade pickup? What is the correlation between Dylos counts of small and large particles and adverse health effects?

And on, and on. Some of these questions may have answers, some will not, some answers will be "depends". I maintain there are too many unknowns, including individual physiology, so we just may have to rely on common sense and best practices when we buy or install a DC (system), and that is where we can run into problems. We need to start with as much information based on solid science and engineering, evaluate as best as possible everything else, and then decide where on the continuum we want to work. Many will be limited by resources others by time, energy, and who a cares attitude?

I wish Bill P's site had a simple and concise section based on non-controversial basics- things all can agree upon. While there will always be a few who won't agree on everything, hopefully enough will agree on some DC "Truths". I'm not talking complex engineering issues, but things such as (and I'm being a bit extreme here) - a single stage dust collector with bags that do not filter below 25 microns may be adequate to collect chips and dust but is nearly useless in protecting your health. Or how about, temps and humidity aside, venting outside, either directly or via separator, rather than recycling air through a bag or cartridge filter, will yield better dust control.

[David Kumm]

Sorry if you took offense.

If particle counters have allowed us, home woodshop enthusiasts, to take at least one giant step forward, then statements like "particle counters can be quite misleading" would be at least two steps back.

I must be reading the wrong thread. I thought Phil was mad and Ian was trying to make up. Dave

[Phil Thien]

I must be reading the wrong thread. I thought Phil was mad and Ian was trying to make up. Dave

My bad.

I thought starting with "Sorry, Phil, I don't think we're getting very far here" and finishing with "anyway - end of thread" was the online equiv. of me telling my wife "Sorry, honey, I don't think we're seeing eye to eye here" and wrapping-up with "end of discussion."

[David Kumm]

Alan, I agree with you but when my allergies make life a pain I turn on the DC and the A/C in the shop and get the best air and best relief of the day. There is more dust in my accounting office than in my shop with the filters running - until I turn on the Oakley. Dave

[David Kumm]

My bad.

I thought starting with "Sorry, Phil, I don't think we're getting very far here" and finishing with "anyway - end of thread" was the online equiv. of me telling my wife "Sorry, honey, I don't think we're seeing eye to eye here" and wrapping-up with "end of discussion."

The only time I expect to say " Honey, end of discussion" and get away with it will be three days before the funeral-mine. Dave

[Phil Thien]

Let me stir the pot with a few random questions

What do the OSHA recommended machine CFM numbers mean? What effect does achieving only 3/4, 1/2, 1/4, etc. of the recommended CFM have on large and small dust particle density at the machine? What are the OSHA recommended maximum small and large particle densities? What are the maximum and minimum exposure times for both? How were they determined and what do they mean? What does it mean if you exceed either? Is there a documented, quantitative direct correlation between dust exposure (both density and time) and adverse health effects or is most of it anecdotal?

To answer your last question first, much (most?) of the evidence IS anecdotal. BUT, anecdotal evidence is often the only evidence we have when it comes to health issues. Until we're all okay with performing extreme scientific experiments on living men, women, and children, we're going to have to rely on anecdotal evidence.

More here:
http://www.osha.gov/SLTC/wooddust/

When using a Dylos, aren't readings taken where the worker is standing (Dylos hung around the neck?) at the time he is using the machine more important than readings taken 10, 15, 20 min. later when the user is sucking much lower (many times lower?) dust densities? What kind of dust density is the user exposing himself to when sawing MDF on a tablesaw that is not equipped with an over-blade pickup? What is the correlation between Dylos counts of small and large particles and adverse health effects?

Without a blade-top pickup? A ton of fine dust. With a blade-top pickup? Well, depending on the blade guard, you may not see any change in Dylos counts with the Dylos hanging right around your neck.

And on, and on. Some of these questions may have answers, some will not, some answers will be "depends". I maintain there are too many unknowns, including individual physiology, so we just may have to rely on common sense and best practices when we buy or install a DC (system), and that is where we can run into problems. We need to start with as much information based on solid science and engineering, evaluate as best as possible everything else, and then decide where on the continuum we want to work. Many will be limited by resources others by time, energy, and who a cares attitude?

I guess this is where I differ from some of you guys.

Particle counters are to woodshop dust control what tire pressure gauges are to properly inflated tires.

We can theorize how much our tires may be under or over inflated until the cows come home.

We might talk about the way the tires "look," or the mileage we're getting. We can look at the wear patterns on the tires.

Or we can just go get a gauge and check the tire pressure.

We don't have to guess. We don't have to wonder. The gauge is in the glove box. We just have to get it and use it to check the tires.

Same thing with wood dust. Just grab the particle counter. Compare your shop to an environment you'd otherwise occupy.

Why make it any more complicated than that?

I wish Bill P's site had a simple and concise section based on non-controversial basics- things all can agree upon. While there will always be a few who won't agree on everything, hopefully enough will agree on some DC "Truths". I'm not talking complex engineering issues, but things such as (and I'm being a bit extreme here) - a single stage dust collector with bags that do not filter below 25 microns may be adequate to collect chips and dust but is nearly useless in protecting your health. Or how about, temps and humidity aside, venting outside, either directly or via separator, rather than recycling air through a bag or cartridge filter, will yield better dust control.

[jim gossage]

Some machines like a cabinet tablesaw or bandsaw, barely have enough "leakage." If the user has blocked off the elevation and tilt slots or under table gaps, and is using a ZCI it can be really bad.

Alan,
Your point got me thinking about the zero clearance inserts that we use for tablesaws. Would drilling several 1/2" holes in the insert improve CFM and also help to bring air past the lower part of the blade, where we want to draw dust off/away from the blade?

[Rod Sheridan]

Alan,
Your point got me thinking about the zero clearance inserts that we use for tablesaws. Would drilling several 1/2" holes in the insert improve CFM and also help to bring air past the lower part of the blade, where we want to draw dust off/away from the blade?

Probably not Jim, as the material you're cutting will block the holes in the ZCI...........Rod.

[Erich Weidner]

Many were actually choosing NOT to use any sort of air cleaner because they were under the impression that they had to capture all the dust at the tool, anything short of collecting all the dust at the tool was failure. "You're breathing the same dirty air as the air cleaner" was the mantra.

I've been reading forums, as well as rereading the Pentz site, and the Taunton book over the last two days. I must admit that the above comment applies perfectly to me. Reading the same material two years ago resulted in my feeling I wasn't doing any good buying the equipment I could afford in the space I had to give up for a dust collector. So... I bought nothing. Just stuck with my fien shop vac. I knew it was inadequate, but I definitely FELT that anything short of a huge noisy tall 5HP cyclone was the only option, and that anything less was no better than my shop vac for fine dust accumulation.

Regardless of how we FEEL about it, it should simply be a matter of fact. And it takes what it takes to clean the air properly. I guess I'm just chiming in to say that "me too, I felt that way".


I'll definitely say that right now I feel like I'm faced with the choice of killing myself (slowely by breathing dirty air) or ruining my enjoyment of the hobby. This is rather depressing to say the least.

(I have only one wall of my garage for my tools and stationary stuff to live, everything else has to be on wheels and be able to fit into 1/2 of the garage at the end of the shop session. Only an 8ft ceiling, so no overhead ductwork for me, no good place to locate the DC, can't mount it outside. I'll probably have to loose my 220v air compressor to add the DC. Or my router table, or my chopsaw table. I already do all planing/jointing with hand tools as there is just no space for more power equipment and I enjoy hand planing.) I wish I could afford a dedicated shop (or even devote the whole garage to it), but that just isn't in the cards. The DC isn't a "fun" thing to purchase, especially when it means giving up something else to install it. But I don't want to die from my hobby so... the quest continues.

I just ordered one of the Dylos particle counters, so I can at least get a feel for what IS in the air of my garage now and will find out if I "guessed" right whenever I figure out what to order.

-Erich

[Darrell Bade]

Was taking a break from just starting to run my ducts and came in and set down for minute. Started reading this thread and then realized I had started it, I did not know it was still going.

Won't say what I am running because that could start it all over again.

I will say that my biggest problem right now is how to get these pipes up to the ceiling and hung by myself. Might just have to wait until I get some help unless my plan works when I go try it in a minute.

[Mike Cruz]

Wait a minute, Darrell... You are hanging your pipes? You should NEVER do that. It is dangerous! You should... Hehe. Have fun getting those things up. An extra set of hands is almost a necessity.

[Kevin W Johnson]

I put 4'x8' sheets of 1/2" OSB on the ceiling by myself. It's all in the technique. Make yourself a stand that will hold the other end.

[Dan Hintz]

I used plastic straps made for hanging pipe... a 15' roll, or something like that, you cut to length. I added way more length to each strap, hung one end up, then lugged the pipe up myself and wrap the second end around and attached to a nail I had previously stuck in the rafter. Go to the other end of the pipe and do the same thing. Go back to the first end and snug up the hanger. Same with the second end.

[ian maybury]

Hi Erich. One option is perhaps that you could consider one of the larger mobile cyclone dust collector and filter units with short hoses that would keep your total pressure drop down to 4 or 5in WG.

It admittedly takes up floor space, but the short hoses (and consequently low pressure drop) mean you should be able to get good CFM from something much smaller than 5HP. Bear in mind that even the larger Pentz style ducted systems usally only draw around 4HP anyway in use - the bigger motor just provides a cushion that protects against overloading if the fan is run e.g. with the ducting disconnected.

On hanging ducts Darrell. I was working in spiral galvanised duct, but mostly alone and found i could build runs of ducting on the floor to measurements - a ladder made a good straight edge against which to do this. (the fits on the spiral i got were sloppy enough that it needed a bit of help until riveted) I then installed the hangers.

Five minutes help was then enough to lift each run of ducting into place for test fitting - the split ring hangers are set up so that when you swing them shut a tab engages to hold them there until the screws are done up.

I used the quick action clips like those found on Nordfab quick connect ducting and the like to make joints between runs as sliding stuff together would otherwise have been difficult. (you can get caught in corners, or between joists in ways that make movement difficult)

You can buy flanged adaptors to suit them that fit on spiral ducting as these from a UK supplier: clips http://www.ducting-online.co.uk/prod...k-Lock-Clamps/ adaptors: http://www.ducting-online.co.uk/prod...Clip-Adaptors/ Using these leaves you with quickly removable joints for future use should the need for clearing out ever arise - but it's best to not rivet the adaptors into the ducts until the joints are made to ensure the flange faces are closely fitted together.

Many of my ducts were squeezed between ceiling joists to save head room, which meant that taping the joints in situ would have been difficult. The combination of the split hangers and the quick clamps meant it was again very easy to disconnect and drop the duct runs in sections on to the floor for taping once their fit was confirmed.

ian

[Darrell Bade]

Mike Cruz said

Wait a minute, Darrell... You are hanging your pipes? You should NEVER do that. It is dangerous! You should...

Given the way that some dust collection threads go, that is funny Mike.

I made progress by myself tonight. I put one end of the pipe on a 8' ladder and then got on a 6' ladder with the other end. My ceiling has metal (pole barn metal) on it so I just loosened a screw or two and temporarily wired the pipe to those screws. Once I get a few sections up I will go back and attach permanently and then continue down the run. Spent most of the time tonight making some standoffs for the drops.