/ Field knowledge · IMC 502.2
A high grille over the hose reels is not 502.2.
Jet-A and avgas vapors are heavier than air. They sit in the compartment, not at the canopy. IMC 502.2: compartments that hold fueling piping, pumps, separators, or hose reels must be ventilated at floor level or within the floor so those vapors cannot pool. A high grille in the fueling room is the miss. Distinct from 502.1.2 fuel-dispensing (≤ 18 in above the floor) — same density, different occupancy.
Educational 2024 International Mechanical Code (IMC) 502.2 from Daily Code Talk. Confirm the adopted edition. Distinct from 502.1.2 (dispensing), 502.16 gaseous-fuel repair (inlets low, outlets high), and 304.5 hydrogen (lighter than air). This is not a hangar design and not a fuel-farm design. Daily Code Talk does not publish a cfm/ft² for 502.2 — so this page does not either. Put “floor level or in-slab pickup” on the schedule and keep it off the house return. Packet: 502.2 PDF · ES.
- The rooms that trigger 502.2 are the ones with piping, pumps, separators, or hose reels — not the passenger lounge next door.
- Pickup is at floor level or within the floor. Heavy fuel vapor does not climb to a ceiling grille.
- Do not treat aircraft fueling exhaust as ordinary environmental exhaust. High concentrations of flammable vapor are a 509 question.
- Do not dump it into the hangar return. Do not manifold it with toilet exhaust.
On the set: tag the fueling compartment, show low or in-slab inlets, and name 502.2 on M-601. If the same campus also dispenses gasoline at a fleet island, that island is 502.1.2 (18 in AFF) — a different row, a different note.
A ceiling fan in the hose-reel room
The vapor is already on the slab. Floor-level or in-slab pickup is the educational check. Pair with 509 if concentrations are hazardous. Hydrogen and CNG invert the story — they rise.
Source: Daily Code Talk — IMC 502.1–502.2 · also Part 2 · tool: Floor-level / in-slab screen · dispensing: 502.1.2 · pits: 502.13–502.15.
What to send
That this is an aircraft fueling or defueling compartment (piping, pumps, separators, hose reels), a section showing inlet height or in-slab pickup, and whether exhaust is dedicated to outdoors.
If the only inlet over the hose reels is a high grille
Send the section. Masterbuild will say whether 502.2 still has no floor-level or in-slab pickup — or 502.2 still treats avgas vapor as hangar return.
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. Floor-level or in-slab ventilation of aircraft fueling compartments (piping, pumps, separators, hose reels) so heavy fuel vapors cannot pool is 2024 IMC 502.2 education from Daily Code Talk — not a hangar design and not a cfm. Fuel-dispensing 18 in AFF is 502.1.2, not this section. This page is not legal advice.