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.

[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.

[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.

[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.

[Maureen Ragan]

, everyone freaks out after reading Bill Pentz' site.

I feel like I'm lost in an underwater cave! My sister laughed at me and said, "It'll take a year for you to figure it all out, and you still won't have a single door or drawer in your cabinets"!

[Ole Anderson]

I also have a 2 hp Oneida Super Dust gorilla. It works fine for me, but doing it again I would opt for the 3 hp unit. Just better specs. As Bill notes, a 7" horizontal main run is optimal with 6" vertical runs if your DC is capable of 1000 cfm with open blast gates. It takes a pretty big offcut to not be pulled up a 6" vertical run. If you think about a 7" horizontal run plugging, think about the increased velocity that will occur at the dust pile as it starts to restrict the flow. That increased velocity will erode the pile and move it down the pipe eventually to the cyclone. Not a problem to worry about. No fires.

Yes, I went with steel 26 gauge snap lock for the ability to run 5" and 7" size pipe as optimal. I have a 7" main run with 6" vertical serving my miter saw and 5" bottom collector on my TS. I use the stud cavity behind the miter saw as a "hood' and vertical duct down to the floor where it is picked up by the 6". Easy to shut the blast gate with my foot. 5" run to my 4" flex to my router table, another 5" drop to my jointer and planer and a third 5" drop to the 4" flex to my 6" x 48" belt sander and my BS.

In my opinion, the fine dust is easier to collect as it doesn't have the momentum heaver particles do when being ejected from a spinning blade, so it doesn't travel as far from the dust inlet.

[Tom Bender]

I'd choose cancer, my wife would treat me better.

[Andrew Seemann]

Also note that the website/resource in question, though likely very well meaning, is also a bit controversial in some quarters, and that it is just one of many resources available. Much of the info is handy and a good guide, but not always universally applicable to all people in all situations.

[Maureen Ragan]

... 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. ....

Thanks so much. I just want to get to work, instead of setting up! Of course, I did a lot of work with just a trash can with directional inlet and outlet attached to a shop vac, so my new system should be better than that!

[Jim Becker]

Yes, you cyclone will do a much better job with the major tools than any shop vac could ever hope to provide. Shop vacs are great for cleaning floors and extracting from small, hand-held tools, but are not capable of doing anything helpful in a big way with larger, stationary tools. The don't move air. They just have high static pressure which is ideal for a small hose and a very small collection port.

Now...go make something.

[glenn bradley]

Thanks so much. I just want to get to work, instead of setting up! Of course, I did a lot of work with just a trash can with directional inlet and outlet attached to a shop vac, so my new system should be better than that!

We all start somewhere. I started with the 5 gallon bucket with a "cyclone" lid . We should all do the best we can but, many of us fall short of the systems that cost more in ducting than the cost of the collector. Even with a full length cyclone I still have activities or areas that put some fines into the air. Hand sanding for one. For these I use a respirator. My previous favorite was discontinued when 3M bought AO Safety.

Safety-001.jpg

My new favorite.

welding resp.jpg

I like a close fitting mask that doesn't put a couple of large filter cans in my peripheral vision. Both are also easy on, easy off and work with my prescription safety glasses and ear muffs.

[Maureen Ragan]

Thanks so much!