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: Type II exhausts at least 1 cfm/ft^2 in dry-cleaning and drying rooms, operates automatically with the equipment, and has manual controls at an approved location. Type IV/V uses automatically activated exhaust to maintain at least 100 fpm through the open loading door. The stated alternative places a hood immediately outside and above that door, with airflow Q = 100 x ALD (loading-door area in ft^2, Q in cfm). Capture spotting and pretreating solvent vapors as well.
502.7 flammable finishes: Provide exhaust wherever flammable finishes are sprayed or applied, including during construction.
502.7.3.1-.2 spraying and recirculation: Run exhaust during and sufficiently after spraying and interlock spraying with ventilation. The default prohibits recirculating spray exhaust. An exception permits use as spray makeup air only with solid-particulate removal, vapor strictly below 25% LFL, an approved vapor monitor, an alarm and automatic spray shutdown when vapor exceeds 25% LFL. If the monitor shuts down, automatically exhaust 100% of the air volume specified in IMC 509. Manned spraying requires all these conditions plus prepared documents demonstrating no life-safety hazard to personnel in the booth, space or room. Check the adopted edition and process.
502.7.3.5-.6 ducts and fans: The default is an independent outdoor exhaust duct for each booth or room. A shared spray duct needs a specific 502.7.3.5 exception: multiple small booths with combined frontal area no more than 18 square feet, identical sprayed material and simultaneous interconnected fan operation when more than one fan serves a booth; or treatment needed for pollution control or energy conservation, with compatible nonreactive/nonigniting materials, no nitrocellulose, overspray filtration and automatic sprinklers at every booth/manifold junction. Keep fan motors outside booths and ducts and apply the permitted nonsparking construction. Dipping, electrostatic, powder and floor resurfacing follow their separate 502.7.4-.7 rules.
502.7.7 floor resurfacing: Provide at least 1 cfm per square foot of the area being finished through approved temporary or portable exhaust discharged outdoors. Keep this distinct from spray-booth and dipping processes.
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 the specific process basis. For floor resurfacing, show the 502.7.7 area times 1 cfm/ft^2 and approved temporary or portable outdoor exhaust; do not substitute a generic room or garage rate.
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/ft² of area being finished for §502.7.7 floor resurfacing, and other rates only where their separate code paths require them.
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.
Model-code source: 2024 IMC Chapter 5. Confirm the adopted edition, amendments, product listing, and project conditions.