Ventilation requirements for automotive repair garages
Ventilation requirements for automotive repair garages
(OP)
I can't seem to find the ACH requirements for a tractor trailer repair facility in NJ. The shop volume is 260,000 cft. The floor area is 3,260 sqft. Fuel will not be dispensed. I recall seeing somewhere that the "recommended" number of ACH is 20-30, which works out to be roughly 130,000 cfm at 30 ACH. Assuming 12 exhaust fans, each would have to exhaust 11,000 CFM. This would present some serious heating and cooling problems for the make up air. Would these run all the time the shop is occupied, or be controlled in some way? Any ideas would be appreciated.
Bill
Engineering Professionals, Inc.





RE: Ventilation requirements for automotive repair garages
RE: Ventilation requirements for automotive repair garages
B.E.
You are judged not by what you know, but by what you can do.
RE: Ventilation requirements for automotive repair garages
Will the space require air conditioning for mechanic comfort?
Utilize source tailpipe capture. This can be difficult due to high exhaust or dual on tractors and low exhaust locations on straight trucks. Rails or hose reels are the best. Utilize 300 to 400 cfm per inlet but base upon fuel/engine size. Utility set with VFD driven on main pressure. Harvey rail.
Check local IMC for exhaust requirement. It will run between .75 to 1.5 cfm/ft2 for exhaust. For tractor repair in bays, I would do 2 cfm/ft2 to avoid issues and account for future fuel changes (natural gas). Operate general exhaust in zones based upon CO /NOx/H. Floating stuff is bad with diesel. You may be required to do ½ of general exhaust as low (6”aff) capture. Utilize a minimum .05 cfm/ft2 continuous – we do .10 with breaker on 24/7 to flush out space. Size direct fired MAU based upon total exhaust flow and operate based upon CO/NOx/H.
Utilize low intensity IR for space heating at service bays. 80/20 direct fired can be cheaper but at lower comfort. You will have to do the math on a machine or machines required. We have utilized both vacuum and positive pressure IR and both have worked well. I like gas unit heaters at overhead doors when utilizing IR for mechanic heating.
For air-conditioned facilities 15 and 20 ton RTUs with concentric packages seem to be the sweet spot. You will lose cooling with the CO/NOx/H & MAU is running but it works out.
Evaluate waste oil for floor heating or radiant floors.
I am located in Chicago so the loads should be similar.
RE: Ventilation requirements for automotive repair garages
The local code authority may want more though.
Always check to see what the code says before doing a bunch of searching.
RE: Ventilation requirements for automotive repair garages
BTW the volume was incorrect. My bad. That's what happens when you rush. Duh!
Thanks to all for feedback. Maybe I can return the favor some day.
Bill
Engineering Professionals, Inc.