Ventilation for welding

[29Tudor]

I have a three car garage, 37’x 26’. I’ve been using one stall on the end of garage for welding sculptures. I’ve been doing this for just a couple years but got into it more last year. I did take the welding outside when weather (wind) permitted, however I did enough inside to coat everything inside with the fumes. Mig welder.
After cleaning everything in the garage I bought an extractor. I had a local shop build a 4’x2’ hood for it. It is only 230 cfm but works fine. I now realize replacing filters is going to be expensive.
My question is if I eliminate the extractor and blow the fumes outside, will I need makeup air and should I use an air to air heat exchanger for the makeup?
I usually weld for short periods, 1-2 minutes at a time.
Garage is pretty tight, well insulated, and I heat it in the winter with a Hotdog propane heater.

 

[mcbane]

If the fan is powerful enough and you provide no means for makeup air, you will draw a vacuum in the garage and eventually it will implode. Or more likely your fan will just no longer move much air.

No idea where you live so it is hard to comment on the potential benefit of a heat exchanger.

 

[29Tudor]

Live in Michigan, so any makeup could be very cold. I may try it without a makeup and then add one if needed.

 

[Copymutt]

I would exhaust it to the outside. & fab a sheet metal air to air exchange plumbed into the base of your work table.

 

[dogdog]

maybe look up the welding fume extractor threads on this forum, there were few from years ago that people build with a HF 8" ventilator and some filters from kitchen exhaust or house hold furnace filters (probably need spark arrestor as prefilter) . Since you already got the hood, just look into how to build a filter box ? I need to make one for a kitchen exhaust for a high rise apartment, just can't find the material yet.

something like these, it's washable.

https://www.amazon.com/dp/B082WNPC1H/?tag=atomicindus08-20

 

[PoorUB]

I have a air cleaner I built from an old furnace blower. I use pleated paper filters and it does a decent job of clearing the air while welding. I just circulate the shop air through it. I don't exhaust any air out side, although I might open the walk in door a few inches if I do some serious welding.

 

[jblnut]

I've been in a few farm shops up here with a sort of solution to your problem. The extractor blows the air outside through let's say an 8" pipe and it is surrounded by a 10" pipe. The 8" pipe has the warm air inside it and it sort of tempers the cold air that returns under vacuum through the larger outside pipe. Think the same concept as what most HE furnaces and boilers use now to vent the gas and bring in fresh air. The piece that sticks through the wall anyway. Now make it all metal so heat can transfer and away you go.

 

[smackdab]

Thats sounds like a great solution to the issue with a double pipe.
On a different note: I'm building a new shop very soon. What I'm trying to conceptualize is running my welding/plasma/grinder smoke under the floor rather than overhead. Was considering placing a grid work of pipe under the floor with hook ups in various spots. Just like whats used for exhaust removal in auto repair shops. Anyone have thoughts on building something like this, and is it feasible?