I want to build a Welding Fume Extractor, any advice?

I am thinking of building my own Welding fume extractor and would like some input from the community. I am a hobbyist and can’t justify the cost of a nice new professional machine. I have a squirrel cage blower fan I salvaged out of a heat pump from a mobile home, I am estimating it is about 1,000 cfm fan. It is 1/3hp. I would like to have it draw across the filters rather than blow. I am thinking of using 3 common home HVAC filters, first a 6 MERV filter then a 14 MERV, and finally a charcoal filter.

I am interested in a fume extractor and not a dust collector. I am very much aware this will not work as a dust collector but my hope is to use it as a fume extractor. This motor/fan that I would like to use will only draw at most ½” of water column, in contrast a dust collector draws probably more than 2”. I have crossed off the idea of a shop vac as I don’t want the noise pollution, further it is more of a dust collector than a welding fume extractor.

Has anyone tried this and what advise do you have? I have spent hours on Youtube and searching the internet and not found much. Yes there are lots of ideas for an exhaust system which I could do however with winter time I don’t like the heat loss of such an idea.

What filter life can I expect from this? Will they stop up in only an hour of welding? I was hoping by having the 6 or 8 MERV filter and then the 14 MERV that I could capture some smoke on the cheaper filter and replace the more expensive 14 MERV less frequently than had I the 14 MERV alone.

Will this 1/3hp motor on a squirrel cage fan draw sufficiently? I am thinking of using a 6” rigid and flexible duct to draw the air to my filter, I don’t want a hood system but rather move my snorkel around to whatever I am welding.

Any advice would be appreciated, I would hope that someone else has tried this before and can say it will work with some modifications or no, save your time and money, it will not work.

I haven't built one, but I've got the Air Flow Systems PCH-1 fume collector. IIRC (it's been a while since I've had my system opened up) the filters are cylindrical, maybe about the size of a 3 gallon can, not as big as a 5 gallon pail. It's very much a high-volume, low-pressure system. The standard collection arm has about an 8" diameter. PCH-1 has one filter and a 1/2HP motor. The PCH-2 has two filters (parallel, not series) and a 1HP motor, pretty much directly doubling the volume through the system.

I use my PCH-1 as a point collector for welding fumes. I have never felt any need to use anything but the standard filter, and I probably clean the filter about every 40 hours of use (which is a lot longer in calendar time). The "Vibra-Pulse" cleaning system just hooks up an compressed air inlet to a rubber hose mounted inside the filter(s). When you hit the clean button, the hose flails around and whacks the inside of the filter cylinder. (The dirt accumulates on the outside of the cylinder.)

I suspect if you stack up 3 filters as you suggest, you'll get effectively no air flow through the system, unless you make it huge, with massive surface area. And the PCH-1 is already the size of a stand-alone machine tool. If you want to use a narrower pipe and push it through three layers of filtering, the high-volume, low-pressure approach is not going to work so well.

Furnace filters absolutely suck. You want a HEPA filter. There are many hepa filters available on ebay in large enough size for your final stage filter.

I don't know what you have for static pressure from your blower but I used a cheap bouncy castle blower to suck through a prefilter and then blow through an automotive intake filter, then a hepa filter, then activated carbon and finally a post filter to catch carbon dust.

This was for a laser cutter that cuts plastic, but the project got scrapped. The extractor works very well though, and I'm sure it would be great for welding.

But rarely do people make dust collectors/fume hoods with enough flow, filtration, and pressure.

A HEPA filter is essential, IMO, but will lower airflow considerably. And filters rated for fine dust also filter fumes well, fumes being gas containing fine dust. I second the multistage approach, though depending on how much you use it, a plain HEPA filter without back purging can serve very well.

Strostkovy said:

Furnace filters absolutely suck. You want a HEPA filter. There are many hepa filters available on ebay in large enough size for your final stage filter.

I don't know what you have for static pressure from your blower but I used a cheap bouncy castle blower to suck through a prefilter and then blow through an automotive intake filter, then a hepa filter, then activated carbon and finally a post filter to catch carbon dust.

This was for a laser cutter that cuts plastic, but the project got scrapped. The extractor works very well though, and I'm sure it would be great for welding.

But rarely do people make dust collectors/fume hoods with enough flow, filtration, and pressure.

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Thanks for your thoughts. I was mostly thinking of using a AC blower as that was what I had available for free. I actually have two of them. I was thinking of setting them up in series where they both are drawing, one and then the other. Thinking on this some more, I could set it up where there would be maybe a MERV 6 and then 14 Furnace filter and then have it blowing through a Carbon Filter and maybe followed by HEPA and then have the second furnace fan pulling on that. Then again this may be too complicated, maybe I need to buy a better fan rather than trying to get by with something I have on hand for free.

I have a clarification question, you said Furnace filters "suck" are you saying they are very inferior in quality or in their ability to filter? Would you please clarify? My biggest reason for using a furnace filter was simply they are cheap, catch what trash I can on a cheap and easily replaced furnace filter from Lowes to extend the life of the more expensive filter down stream so to speak. If you have some further wisdom to share on my idea I would be happy to hear.

Steven

Welder want 2 be said:

Thanks for your thoughts. I was mostly thinking of using a AC blower as that was what I had available for free. I actually have two of them. I was thinking of setting them up in series where they both are drawing, one and then the other. Thinking on this some more, I could set it up where there would be maybe a MERV 6 and then 14 Furnace filter and then have it blowing through a Carbon Filter and maybe followed by HEPA and then have the second furnace fan pulling on that. Then again this may be too complicated, maybe I need to buy a better fan rather than trying to get by with something I have on hand for free.

I have a clarification question, you said Furnace filters "suck" are you saying they are very inferior in quality or in their ability to filter? Would you please clarify? My biggest reason for using a furnace filter was simply they are cheap, catch what trash I can on a cheap and easily replaced furnace filter from Lowes to extend the life of the more expensive filter down stream so to speak. If you have some further wisdom to share on my idea I would be happy to hear.

Steven

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Furnace filters make a great prefilter but they allow many smaller dust particles through, and you will produce lots of fine dust. Two blowers may handle both filters.