Plain English:
502.2 aircraft fueling/defueling: Vent fueling compartments at floor level or within the slab so heavy fuel vapors cannot pool.
502.3 battery charging: Exhaust powered industrial truck/equipment charging areas to prevent flammable gas buildup.
502.4-502.5 stationary batteries: Vent battery rooms and cabinets per IMC 502 and fire code so off-gassing stays controlled.
502.6 dry cleaning: Vent to control solvent vapors. Type II: 1 cfm/ft^2 in dry-clean and drying rooms. Type IV/V: exhaust based on loading-door area or an exhaust hood sized to that opening.
502.7 flammable finishes: Provide exhaust wherever flammable finishes are sprayed or applied, including during construction.
502.7.3 flammable vapor areas: Run exhaust during and after spraying so vapors clear. Interlock spray equipment so it cannot run without exhaust. Spray exhaust is normally not recirculated; any recirc must keep vapors below 25% of the lower flammable limit (LFL) with monitoring and auto shutdown.
502.7.3.5-502.7.7 ducts, fans, and other processes: Give each spray booth/room its own exhaust to outdoors unless strict manifold rules are met. Use non-sparking fan wheels, keep motors out of the airstream, and ventilate dipping, electrostatic, powder, and floor-resurfacing ops so vapors stay well below hazardous levels.
On Plans: Why it matters
These spaces trigger IMC + IFC; "EXHAUST AS REQUIRED" with no cfm/ft^2, velocity, or controls draws redlines.
Code Path: Where to show it
M-001: "SPECIAL PROCESS EXHAUST-IMC 502" note with simple design bases (1 cfm/ft^2, door face velocity, low inlets, interlocks).
M-101: Tag special-process rooms and show inlet height (LOW/HIGH) and independent ducts to outdoors where required.
M-601: Exhaust schedule with EXHAUST TYPE, DESIGN BASIS, and CODE REF for these spaces.
Check: Do
Ask what each space actually does (spraying, dipping, batteries, resurfacing) and design to the process, not just the room name.
Match pickup height and design basis to the hazard: low for heavy vapors, face velocity at doors for spray, 1 cfm/ft^2 where required.
Review Risk: Don't
Lump these into generic "EXHAUSTED ROOMS" without a process-based note.
Recirculate spray/flammable-finish exhaust or manifold it with environmental exhaust unless every code condition is clearly met and documented.
Field Tip:
On M-601, add a "SPECIAL PROCESS EXHAUST-IMC 502" schedule with ROOM, PROCESS, EXHAUST TYPE, DESIGN BASIS, and CODE REF so reviewers see you designed for the hazard, not just the room tag.
Masterbuild QA Lens
Product-conveying duct material must match the contaminant classification and the Section 510 or Section 511 requirements as applicable. Galvanized sheet metal that is acceptable for general exhaust is not acceptable for corrosive or combustible product streams. Confirm the material basis on M-001 and cross-reference the listing or standard that qualifies it.
Drawing / Submittal Check
For special exhaust systems (502.2-502.7.7): the drawings must identify the specific space type (parking garage, corridor, laboratory, etc.) and the code table row that establishes the exhaust requirement. Exhaust rates, makeup air, and any special requirements (standby power, alarming) must be explicitly shown. If exhaust from a special space combines with general exhaust, confirm the combination is permissible under IMC 502.
Common Review Risk
Special exhaust system comments concentrate on the exhaust rate - projects that use the general ventilation table rate instead of the specific table rate for the space type. Parking garages, semiconductor fabs, and spray booths each have specific ventilation rates that are higher than the general exhaust table. Applying the wrong row to the wrong space is a common error that requires a fan size change when caught.
When To Escalate
Escalate for parking garages with CO monitoring, for laboratory exhaust systems with variable sash positions, and for any special exhaust application where the ventilation rate must respond to a real-time sensor input. These systems require controls coordination between the mechanical, electrical, and controls disciplines that cannot be handled with a standard design.
Special Condition-Battery Rooms
For battery rooms or charging areas, confirm the battery type, hazard basis, ventilation calculation, control sequence, alarm interface, exhaust path, and AHJ or fire-protection coordination are all traceable. The drawing set should not leave the safety logic implied.
Load Assumption Check
Special exhaust systems (502.2-502.5) for specific occupancies have minimum exhaust rates set by the code, not by comfort load. Confirm the exhaust CFM on the schedule meets the code minimum and that the makeup air system is sized to replace that exhaust volume.