Title 24 Requirements for Auto Repair Shops
An auto repair shop is decided by its exhaust. Table 120.1-B sets auto repair rooms at 1.5 cfm of exhaust per square foot, among the highest rates in the table, and the code closes off the usual way of turning that ventilation down.
- Send your plans
- Get a free quote
- Approve it
- Report in 4–5 business days
The exhaust rate comes first
Section 120.1(c)4 sizes exhaust from Table 120.1-B, and auto repair rooms carry 1.5 cfm per square foot — more than twice a commercial kitchen's 0.70 and three times a barber shop's. The air drawn in to replace it may be outdoor, recirculated or transfer air in any combination, and the Compliance Manual is clear that the rate holds whenever the space is expected to be occupied.
The table adds a note that matters on the shop floor: stands where engines are run need an exhaust system connected directly to the engine exhaust, so fumes do not escape into the bay.
Turning it down is restricted
Demand control ventilation is the normal way to cut outdoor air in a lightly used space. Section 120.1(d) withholds it from spaces with processes that generate fumes and no local exhaust — the code's own example is indoor operation of internal combustion engines — and Section 120.1(d)3 says such spaces shall not install it at all. A CO2 sensor tracks people; it says nothing about exhaust gas.
Class 2 air, and what shares a system with it
Auto repair rooms are Class 2 air, which may not be recirculated or transferred into Class 1 spaces. The Compliance Manual names auto repair rooms when it says a system serving Class 2 air should not share an air handler with Class 1 spaces, so the customer lounge and the service office normally need their own. A paint spray booth is Class 4: no recirculation at all, not even within the booth.
Lighting: a task allowance and a boundary
Auto repair and maintenance areas are their own function area in Table 140.6-C, with an additional allowance for detailed task work. It has to be earned: the task areas and the luminaires serving them must be shown on the plans, tasks done for less than two hours a day do not qualify, and general lighting fittings cannot be counted towards it.
Where the bays are unconditioned and the front office is conditioned, the two cannot trade allowance. The area category method permits trade-offs between areas, but never across the line between conditioned and unconditioned space.
Where to go deeper
How the outdoor air quantity itself is calculated is covered under commercial ventilation. A workshop that also sells cars should read the dealership requirements, where the outdoor sales lot changes the lighting picture.