/ Field knowledge · IMC 502.13–502.15
A CO sensor on the parking floor is not the pit.
A lube pit is not “the garage, but lower.” IMC 502.13–502.15: public garages exhaust continuously or per IMC 404 + 403. Where Class I liquids or LP-gas can reach a basement or a pit, provide exhaust that keeps flammable vapor from building up in that hole. A CO sensor on the parking floor does not ventilate the pit. A wall fan at the office does not either.
Educational 2024 International Mechanical Code (IMC) 502.13–502.15 from Daily Code Talk (same post as 502.11–502.20). Confirm the adopted edition. Distinct from 404 enclosed-garage ventilation (the floor above), 502.14 tailpipe capture (engines that run in place), and 502.16 gaseous-fuel repair. This is not a pit design and not a cfm. Daily Code Talk does not publish a pit rate here — so this page does not either. The question is whether vapor that can pool in the hole has a dedicated exhaust path. Packet: 502.13–502.15 PDF · ES.
- 502.13–502.15 public garages: exhaust continuously, or the 404 + 403 path. “We have a CO sensor” is not, by itself, the 502.13 sentence.
- Basements and pits that Class I liquids or LP-gas can reach: exhaust to prevent flammable-vapor buildup. Gravity will put the spill in the pit. The drawings have to put the inlet there too.
- Do not call the parking-floor 404 system “the pit exhaust.” Do not dump pit exhaust into the house return or the toilet shaft.
- If engines also idle on the floor above, that is still 502.14 (hose on the tailpipe). Two different rows. Two different notes.
On the set: tag the pit or basement, show a low inlet in the hole, and name 502.13–502.15 on the schedule. If the AHJ asks for 404 numbers on the parking floor, send them to the 404 page — this page is the hole.
An oil-change pit with no exhaust in the pit
Or a basement parking stall under a repair shop, with the only fan on the floor above. Class I liquid and LP-gas vapor sit low. The pit is where they go. Exhaust that never enters the pit does not count.
Source: Daily Code Talk — IMC 502.11–502.20 · tool: Pit / basement screen · 404: garage · tailpipe: 502.14 · aircraft: 502.2.
What to send
That there is a pit, basement, or oil-change hole; whether Class I liquids or LP-gas can reach it; and a section showing an exhaust inlet in that volume — not only on the floor above.
If the pit has no inlet in the pit
Send a photo of the hole and the nearest fan. Masterbuild will say whether 502.13–502.15 still has no pit exhaust — or 502.13 still treats the parking-floor 404 system as the pit.
Send Project Background+1 (786) 398-6940 · osmany.portal@masterbuildconsulting.com
Masterbuild provides engineering services under a written scope. Nothing on this page is project-specific engineering advice, a code interpretation for your project, or a representation about permit approval. Confirm the adopted edition. Public-garage exhaust continuously or per 404 + 403, and exhaust where Class I liquids or LP-gas can reach basements or pits so flammable vapor cannot build up, are 2024 IMC 502.13–502.15 education from Daily Code Talk — not a pit design and not a cfm. Parking-floor 404 and tailpipe 502.14 are different rows. This page is not legal advice.