Dust Collection – Burn down the house or get lung cancer, which should I choose?

[Maureen Ragan]

I wish I’d read Bill Pentz’s site BEFORE I bought my Grizzly 0861 2HP cyclone dust collector, but now I must do the best I can with what I have.

According to Bill Pentz, either:
a) I use 7” duct thereby getting my 1000 cfm and fine dust removal, but worry about dust piles in the line OR
b) I go with 6” duct and leave the fine dust in the air.
Hmmmm, … burn down the house or get lung cancer – what a choice!!

So, I’m trying to figure out two specific issues:

1) What size should my main duct line be (6” or 7”)(see detailed questions below), and

2) Confirmation of my belief that one should never downsize at a tool, but instead modify the tool’s outlet using wyes so that the sum of the tool’s outlets equals the area of the duct line.

1a) Main duct line. Bill Pentz says that on today’s dust collectors the 7” duct line will not have enough pressure to generate the air speed needed to keep vertical lines from plugging. He recommends a minimum of 4000 fpm. Grizzly says the 7” inlet of my collector has about 3500 FPM, moving 1023 cfm with 1.2 static pressure.

So my question is, if I decided not to run my duct line up to the ceiling with down drops, but instead, roll my tools over to very short lines that have a maximum vertical drop of 3' can I use the 7” duct without getting dust accumulation in the line? If so, I could get my 1000 cfm without burning down the house.

1b) If I have to decrease to 6” pipe to increase velocity, at which point should I reduce? Right at the inlet to the dust collector using a 6” main? Use a 7” main and reduce at my branches? Use 7” main and branches and reduce at the tool? I’m guessing this will all depend on the resistance in the lines of the various options and there’s no simple answer.

2) According to Bill Pentz, there’s never a reason to reduce a port at a tool below the duct line, right?

This is my first post and my first dust collection plan for my shop, so please forgive any mistakes.

Thanks so much,
Maureen

[Jens Hoffmann]

Can you elaborate on b) a bit? I know very few people who have a main duct line that's larger than 6" and nobody has burned their shop down yet (that I know).
I guess the real question is:
- What are your personal requirements? What are you trying to achieve? What equipment do you have, how big is your shop, and what are you and are you not comfortable with when it comes to fine dust?

That's where I'd start... You can get really sucked down a rabbit hole if you are trying to eliminate all possible dust. Soon enough you're thinking about a 20 HP, $45k industrial unit that has to live outside due to the sheer size of it.

[Jim Becker]

That unit has a 7" inlet. (as does my 2hp Oneida cyclone) For practical reasons, you can do as I did and run 7" initially to the inlet and utilize 6" duct from the first major branch. You will be "splitting hairs" to try and "optimize" everything with such a small system. My cyclone probably has, oh...about 7-8 feet at 7" and is 6" beyond that. Performance is just fine. No way would I continue 7" on a 2 hp system beyond that point. My drops are a combination of 6" to the J/P (big chip/dust producer) and 5" to major tools that have 120mm ports and my floor sweeps. 4" drops are used to things like my CNC and router table.

And be wary of static vendor statistics on dust collection systems...you need to look at an actual fan curve to compare performance over a range of "real/typical" conditions.

You are not going to burn down your shop with your dust collection system, BTW, unless you're collecting burning things from the tools.

[Maureen Ragan]

Yes, the 6" main line is the choice that prevents burning down the house. But 6" achieves only 710 cfm on my dust collector, so that means I don't have the 1000 cfm minimum to get the fine dust out of the air.

[Jim Becker]

Since you can only move so much air with that particular cyclone system, you'll have to either live with it and use additional methods to help filter fines in the are as well as use a respirator when appropriate or buy a much larger collector that can maintain the air volume you want to move in the system. It's a money choice, pure and simple. Also please keep in mind that the resource you are quoting had a very, very high sensitivity to airborne dust due to his own health conditions. His advise is certainly sound around the ideal, but we each have to choose our own paths relative to how far we want to go with things. I'm happy with my system. Would I buy a larger one today? Yea...I probably would given how I've expanded my shop. But most of my personal dust concerns are not with tools like my table saw and J/P. It's around things like hand sanding because that's been the one place where I generate fine dust that's less contained, unlike when I'm using my powered sanders that have excellent extraction. I'm building a down-draft table to bridge that last frontier.

[Maureen Ragan]

You are not going to burn down your shop with your dust collection system, BTW, unless you're collecting burning things from the tools.

Thanks. I guess lung cancer it is. I guess I need to research really good masks.

[Greg Parrish]

My shop is small but I’m running 6” duct straight out of my 3HP Oneida V3000 with an immediate 7” to 6” adapter and a 45 degree angle followed by a 6” wye. From there it continues to the ceiling and then branches off in two directions to about 6 different gates. I used 6” pvc. Aluminum lee valley gates. And 5” flex to most of my tools. The cnc has 4” and saw over blade has 3”.

long story short my system in a 22x20 shop will lift solid wood from ground to ceiling, across the room and down into the cyclone. On occasion if the piece is big enough I have to open other gates to get it moving across the ceiling.

but over the years, after pulling it all down and reconfiguring it numerous times the only spot I’ve found any accumulated saw dust is where I had a capped off wye that faced down instead of being level with the line. Had it had a gate that opened it would have been dust free too.

way too many other dust issues in the shop than to worry about this one based on 6” vs 7” pipe. Bigger concern is capture at the source I think. Learned this first hand after standing near my cnc while it cut mahogany. No other tool bothered me but the cnc apparently wasn’t collecting all of that free dust as I ended up with a sinus infection that I think was dust induced.

[Jim Becker]

Thanks. I guess lung cancer it is. I guess I need to research really good masks.

There is always risk, Maureen. Your cyclone is only one part of multiple ways to mitigate risk from dust. Unless you're doing all your surface finishing work with sharp hand planes, your biggest risk for dust is when sanding. Keep that in mind as you outfit your shop and choose how you're going to make it a pleasurable space to work in.

[David L Morse]

Thanks. I guess lung cancer it is. I guess I need to research really good masks.

I know that nasal cancer is associated with high levels of wood dust but I haven't heard about lung cancer being a risk. Do you have a reference for this?

[Maureen Ragan]

Thanks so much!

[Jim Becker]

As an aside, thanks for joining SMC as a Contributor, Maureen! It's a great community and I have no doubt you'll not only get a lot out of it, but give folks things to think about, too. Welcome!

[Kevin Jenness]

My experience aligns with Jim's. I used to run a 2hp Oneida blower with ducting designed by Oneida using a 7" main and 4", 5" and 6" drops depending on the tool hood size. The fan performance curve with cyclone they supplied showed 950cfm@1" s.p. and 675cfm@5" s.p., probably comparable to yours. It worked ok, a little weak on pulling all the chips from a heavy cut on the 16" planer. As long as the filters were clean there was no buildup in the main duct. I upgraded to a 3hp blower when I added a cnc router at the far end of the shop, and overall performance is better. I run an ambient air filter as well.

If you want better performance, dig deeper in the old fruit jar and upgrade to a 3 or 5hp system. If you have room, stay away from cartridge filters in favor of felt bags/tubes with a high area/cfm ratio. But you can get adequate performance with your existing setup- I don't think you have to choose between arson and cancer.

[Andrew More]

Bigger concern is capture at the source I think.

Agree 100%. A nicer collector will move more air, which will help with this, but you really need to look at what can be done at the individual tool. You also have to realize that it's a bit of a fool's errand to attempt to capture 100% of the dust.

Just look at the challenges inherent with a sliding compound miter saw, or a table saw. In either case you have a blade with tips moving at ~100+ MPH, while the best Bill Pentz design hits like 40 out of the tube and drops exponentially the further away you move. In the case of a sliding compound miter saw, you also have a saw that has a great deal of flexibility in it's positioning, making collection virtually impossible.

Some dust collection is a good idea, particularly if you deal with wood that's a sensitizer like cedar, or rosewood, but you need to balance this out with other priorities as well. The answer for a weekend wood worker doing things occasionally for fun, and not doing production 40 hours a week is very different from a professional with constant exposure.

Here's a good list of woods that are more toxic than others:
https://www.wood-database.com/wood-a...-and-toxicity/

[Bob Riefer]

I can remember going through the same feelings when first learning about this.

For me, it came down to:
- I do the best I can with the amount I can afford (currently 3 hp blower, onieda cyclone, wynne cartridge filter, 6" pipe with shortest possible runs, minimal bends and step downs... plus an extra ambient filter... all this about $1000 total)
- I regularly clean out my shop with broom, shop vac, and sometimes an electric leaf blower
- I wear a respirator when doing especially dusty work (e.g. sanding, cleaning the shop)

And for peace of mind, I remind myself that we're all constantly breathing various pollutants in... pollen, car exhaust, dust mites, second hand cigarette smoke, pet dander, campfire smoke, paint fumes etc. etc. It's just not possible to have perfect air. I'm in my shop about 10 hours a week, and am doing the best I can to be healthy, but am also optimistic that the human body can handle some adversity (especially since I'm giving it the ol' college try).

[Patrick Kane]

I do wonder what the actual associated risks are. I know Bill has severe issues, but they seem very very rare. From what i remember, he had issues prior to woodworking, and his unique condition was not caused by woodworking, just exacerbated by it.

Id recommend as Jim does to go with 7" down to 6" quickly. 7" fittings are somewhat unusual an they are more expensive and harder to come by. I run a 7" main line off an 8" inlet, but all my branches go down to 6" simply because my tools are 6" ports or two 4" ports and the blast gates, wyes, etc are easier to source in 6".

A few things: One, everyone freaks out after reading Bill Pentz' site. It is intimidating stuff. For the most part, i think most would agree a 3-5hp cyclone with merv 13+ filters and 6-7" ductwork would protect most hobbyists pretty well. Say, reduce your exposure to harmful dust by 80% compared to a shop with no dust collection. Wearing a properly fitting mask by 3m or others takes care of the remaining 19.9% of exposure risk. I used to wear a full face shield and respirator all the time, but they are very uncomfortable to live in for prolonged periods of time. Not to mention the summer months killed me, and i was in AC! I now mostly rely on the cyclone, wynn filter, and air cleaner with a wynn filter. I think the more harmful aspects of woodworking exposure are the chemicals. I would be very mindful of what finish you use, epoxy, the urea resign glues etc. Spraying conversion varnish without a proper respirator and ventilation is significantly worse for your health than cutting some domestic hardwoods on the weekend with a 2hp cyclone DC. My last point is, i know a handful of cabinet makers, furniture makers, or millwork guys that are in their late 70s or early 80s, and they seem to be fine. That is a lifetime of being in a shop setting with poor to mediocre dust collection. Oh, and a few of those chaps were processing MDF and other harmful man-made products. They breathe fine and i dont think they have asthma. Now, will it maybe catch up with them over the next decade? Maybe. However, if you arent doing this full time in a negligent manner, i really think the dust exposure has minimal risk. For example, i rarely wear a respirator while woodworking. Always fully protected while spraying water bourne finishes.