So I'm in the process of setting up a small fabrication shop in an extra garage(as a business) and am currently trying to sort out how much ventilation I need. Up here in The Great White North of eastern Ontario, daytime its not getting much warmer than 10* Celcius (50F) and dropping as low as freezing overnight. We're in the final push to insulate, drywall, and seal up before the winter, and keeping the garage door and windows open is no longer an option.
I'm having no luck finding any specific tables or official info re: how much ventilation is needed. I bought a wall mount fan made by CanArm that can suck out 1850 CFM. I didn't notice till I got it to the shop, but the box had a chart on it that gave various examples of times req'd for total air exchange. The example calculation was for a garage 36x36x10, so 12960 cubic feet. The required air exchange time for a GARAGE was stated to be 5 min.12960 CF / 5 min = 2592 CFM. Look up the model that draws equal to or more than 2600 CFM and Bob's yer uncle.
The chart on the box suggests that a WELDING SHOP should exchange its air every 2 min.When the ceiling goes in this week, the volume of the shop will be 8410 CF (29x29x10). My fan will only do it in 4 and a half min. For small work I've already built a fume hood over my2.5x4ft welding table that probably draws about 250CFM. So the concern is work done in the middle of the shop on trailer frames etc. --BUT-- I'm the only welder, so the worst case scenario is me stick welding and my partner MIG tacking things together at the same time. This is not a production welding shop with rows of welding booths, each one manned with an arc welder running all the time.
I'm mounting the fan in the attic gable and building a large duct in the attic to connect the fan directly to the 22x30" opening in what will be the ceiling(approx. centred in the middle of the shop).
Do I really need to get my air exchange rate down to 2 minutes? Buy the bigger Fan?
Thanks in advance.