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I Forge Iron

Air cleaners

Etienne Gregoire

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It is amazing how much a 450 sq.ft. "studio" with an 8 ft. ceiling can pack up with grinding dust and welding fumes when all doors are closed!
This is the first winter I spend in my shop and I simply didn't see that one coming...

I do have an exhaust fan that I run every 20 to 30 minutes to change the air but it's "super Canada cold" outside and I throw all of my heat out.

I am looking for a way to purifiy my air without having to throw it outside.
I also wish to be able to contain the fumes inside the shop for our house is just next to it. We now have a little baby girl and it freaks me out just to think that I could intoxicate her.

Is there an affordable solution adapted to a small shop like mine?
Most of the systems I see I can't afford right now (welding fume extractors, etc.)

Maybe the kind of air cleaners you can get for a few hundred dollars and that are primarely designed for wood shops?

Thanks for your help!


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For the dust, how about an old, large fan (or several)? Make an open ended box to put it in, and attach filter media to the inlet end. If there's an air conditioning suppliers near you, they'll sell filter media or be able to sugest somewhere that will & it's not really expensive. I'd recommend at least F4 & preferably F5 filtration.
Just stick 'em up in your smithy so the dirty air gets drawn over the filter & the clean air recirculates around the shop.

For the fumes, perhaps you could score an old fume cupboard or similar? Would running an extract fan with a water bath on the outlet side work, like some do with their coal forges? Sorry, I'm in A/C as you may have guessed, but fume extraction / treatment isn't something I've been involved in.

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Let us think outside the box for a minute, literally. Take the grinding and welding operations outside so the dust and fumes are no longer a problem. You will be surprised at the color of the snow in the work area, as it will turn gray (grin).

A flex duct connected to a fan will exhaust from the point of use to the outside. It will remove a lot of the welding smoke.
You can build a box (read horizontal hood) at the edge of the work table and aim the sparks toward the hood. A small fan via flex duct to the outside will extract a lot of the dust problem.

Several years ago there were electrostatic participators that were stand alone units about the size of a box fan. They worked very well for indoor environments, and only need water to clean the plates (remove the dust) on a regular basis.

The best answer may be a combination of many suggestions.

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Dress for the cold air.

Install a radiant heater, then the cold air is less of an issue.

There are heat exchangers that warm incoming air with exhaust air. This way you can circulate air better with the exhaust fan always on.

Use point of use dust collection to a filter that is outside. This way the dust is removed by vacuum with less air than a hood requires. Removing the work to outside will work better.

Box fans with furnace filters will remove general dust from the air, but the filters will clog quickly. A washable pre-filter will probably help.

There are a number of industrial options that exist, with industrial price tags attached.


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I DO fume, dust and vapor exhaust as a factory safety guy. Here are a few tidbits to help.

1. Fume is smoke, ie welding smoke. This is microspocis sized metal droplets that freeze and then are so small they can float. These are dangerous to the lungs, as they get by the bodies natural defenses.
2. Vapor will go right thru most dust and fume filters. Vapor is evaporated liquids such as paint solvent.
3. HEPA filters are rated to protect the lungs from stuff too small to see, and those are the particles that harm you. Most of the bigger dust that you can see hit the ground and never get inhaled. In asbestos, the fibers that get into the lungs and cause the grief are about 1 micrometer by 4 micrometers in size. We can't see things below about 40 micrometers.
4. A furnace filter if of the pleated type is better than nothing, but just barely.
5. Most furnace filters and woodworking dust colletctors are a fire waiting to happen in a metal shop as the filter media is not spark rated.
6. Most grinding dust collectors are of the "Roto-clone" variety and draw the air in and down into a water bath. The air is coming down and has to make a hard 180 degree turn to rise back up and out of the machine. The dust particles have too much mass and can not make the turn but rather go straight and impact the water.
7. If you plan to work in a closed shop, one that is heated, and not blow all the air out, use point of generation capture. A good but fairly small blower, with a flex duct is placed close to wear the dust is made. You need 100 foot/sec velocity, AT the point of generation by the suction and you will capture the dust,smoke vapor etc.

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