Modified fume extractor using furnace blower

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I heard that a metal artist set up a used furnace blower at her work station to pull fumes off and out of the shop. Anyone familiar with this concept or others that I could build vs buying a $$$ fume extractor?
Reply:Are you paying for heat this winter??  -- is a shame to pump it  all out side . . . . Might work ok in summer if your shop isn't air conditioned, though.  I don't know much about extractors, but I believe most filter the air and return to the shop.   The filters are probably a good part of the cost-- fredLincoln 180C MIG
Reply:You are spot on.  I now recall that the artist works in an unheated shop, so summer venting is ok with her. Yes I heat mine--radiant in the concrete.  And yes the fume extractors return the much filtered air inside the premises.  Maybe I could build a box to hold a nest of charcoal filters.
Reply:If you don't want to lose the inside heated/cooled air to the outside, you need a heat exchanger - coaxial ducts, with air going out one and coming in the other so the incoming air is heated/cooled by the outgoing air.  The outside ends should be separated several feet so the extracted fumes aren't immediately drawn back in - the outgoing duct should be above the intake duct because the exhaust air is likely hotter than the intake air.  The length of the heat exchanger section is dependent on the duct diameters and the cfm of the blower.  You probably don't need a 1200 cfm blower (ballpark size for a forced air furnace).  Example: your welding table is 4 x 6 feet and the fume extractor hood is 3 feet above it.  The potential cubic feet of space between hood and table is 4 * 6 * 3 = 72 cubic feet.  A readily available muffin style fan rated at 100 cfm could potentailly replace the air above the table every 45 seconds - the furnace blower would move that much air every 4 seconds.   This isn't a sealed system, so these are "back of an envelope" calculations but are good enough for making comparisons.The outside duct ends also need some type of "critter" mesh and the ends should either be turned down or "roofed" to prevent rain/snow entry.John
Reply:This is why I didn't bother with heaters in my shop. Mind you, I'm in Victoria. Don't get super cold here for long periods. If needed, I'll use a tank top cat heater under the weld table. 500w halogen work light, at your back works toasty too!I'm going to build an extractor arm when I get time. Got 6" spiral duct and an in-line axial fan. Had the builder install a few 6" dryer vents in the walls to duct out. I would see what you can get at the local hardware store in charcoal filters and build a filter box if you want to vent inside. Plywood is cheap.200amp Air Liquide MIG, Hypertherm Plasma, Harris torches, Optrel helmet, Makita angle grinders, Pre-China Delta chop saw and belt sander, Miller leathers, shop made jigs etc, North- welders backpack.
Reply:Just make sure that if you're a business, you're meeting OSHA and EPA requirements.What was a simple HVAC setup at one of our projects turned into individual exhaust units, spark arrestors, environmental filters, and a HAZMAT company to come clean the filters and dispose the collected particulate...
Reply:the effective extractors are hepa filters, not sure that charcoal will work..any homemade heat exchanger will probably have a lot of resistance to flow necessitating lots of fan and have a lousy effficiency..