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shop ventilation


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I am finishing up my garage shop and have been looking into proper ventilation.  I have a squirrel cage blower from my old forced air house heater. Good CFM rating.  Do I mount the motor on the outside and suck the air out or mount it on the inside and blow it out.  My concern with blowing out is it could, in theory, blow hot air into the walls.  If it's outside it would be on a platform mounted to the side of the building.  The building is standard wood frame construction and vinyl sided. 

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I zadvorney there's a few things to consider , first if your only using the fan for room ventilation only  there would not be so much an issue with heat and a section of steel ducting through your wall penetration would stop air going into a wall cavity. I would prefer to have to fan assembly inside and duct the air out ,there may be a problem with noise if its mounted on the side of the building and some of those motor are not weather proof. Electrical connection would also be easier. 

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  • 3 weeks later...

 I will need to exhaust my shop also, fumes from welding , the forge both coal and gas, plus cleaners and paints and at times engine exhausts. I will have to determine how many cubic feet in the shop and what the recommended air exchange for my shop, and what I'm doing in there, this will tell me how many C.F.M. I would need. Then I can get the right size exhaust fan.

                                                                        Adirondacker

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Exhaust is tricky, remember that you need to have a source for makeup air for any anticipated exhaust.

Current NYS code is for 1.5 CFM/SF for repair garages, though a formal engine exhaust system should be installed if this is a regular operation.  For limited spraying of paint the requirement is for a total of 6 air changes per hour (ACH) with a system that meets the NYS Fire code for handling flammable vapors.  Welding fume extraction rates are dependent on the type of hood used (stationary for a work bench, or a mobile arm).  Typical capture velocity is around 100 feet per minute of hood inlet crossection.

Coal and gas forges depend on the size of the hood for the former and the combustion product outlet (based on burner characteristics) for the latter.

Typical selection for a forge exhaust fan would be a high airflow, low static fan.  A sidewall propeller type with a gravity (barometric) outlet damper to seal the opening when not in use is often a good choice.

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  • 3 weeks later...

Thank you Latticino.  I built a hood for the outside and it covers the damper.  The supplied air comes from an open man door on the front o the garage.  I dunked a piece of hot steel into an oil bath and let smoke fill up the room.  Turned on the fan and it all left in a hurry.  I'd have to do the calculations but I'd bet I'm close to the 1.5 CFM/SF. I leave the fan on low when forging and bump it up when welding.  I'll post a picture of it tomorrow.  

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