Daily Code Talk — IMC 502 Summary (Required Exhaust Systems)

🧠 Plain-English Highlights• 502.1 general: If a process makes “bad air” (dust, fumes, heat, vapors, spray, smoke) that can irritate or affect health/safety, IMC 502 says you owe exhaust – even if Table 403 doesn’t name the room.• 502.2–502.7 special processes: Aircraft fueling, battery charging/rooms, dry cleaning, flammable finishes, spray booths, dipping, electrostatic, powder coating, and floor resurfacing all get specific exhaust rates (cfm/ft², face velocity) and “run while the process runs” rules.• 502.8 hazmat: Over maximum allowable quantities (MAQ), storage and use areas need hazmat exhaust (often ≥1 cfm/ft², usually continuous), emergency shutoff, pickup height based on vapor density, and no recirculation of contaminated air to occupied spaces.• 502.9 specific materials: Adds extra rules for medical gases, corrosives, cryogenics, flammable/combustible liquids, highly toxic/toxic liquids and gases, ozone, LP-gas, silane, etc. Think local capture at the source, 200 fpm at gas cabinet/enclosure faces, and scrubbers where leaks or spills can create dangerous vapors.• 502.10 HPM + 502.11–502.20 special occupancies: HPM fabs, gas rooms, gas cabinets, projector rooms, organic coating rooms, garages/pits, gaseous-fuel repair, tire recapping, firing ranges, and mani/pedi stations all need purpose-built exhaust with defined rates, pickup locations (low/high/local), and sometimes interlocks.🏗️ Why it matters• IMC 502 is where “normal” exhaust stops and special/hazardous exhaust begins. Missing MAQs, process exhaust, or treatment plans is a common plan-review stall.🗺️ Where to show it• M-001: “IMC 502 REQUIRED EXHAUST” note listing key triggers (process rooms, hazmat, HPM, special occupancies) and that design is based on cfm/ft², cfm/lamp, or face velocity as applicable.• M-101: Tag special and hazmat/HPM rooms and show LOW / HIGH / LOCAL pickup or source capture.• M-601: “IMC 502 REQUIRED EXHAUST” schedule with ROOM, PROCESS, EXHAUST TYPE, DESIGN BASIS, and CODE REF.✅ Do• Ask what actually happens in each room and check it against IMC 502.• Coordinate early with architect and fire protection on MAQs, NFPA 704 ratings, room ratings, and shafts so IMC/IBC/IFC all tell the same story.⛔ Don’t• Recirculate exhaust from spray, flammable finish, hazmat, HPM, or firing range systems unless every code condition is clearly met and documented.• Combine these exhaust streams with general return or environmental exhaust.🔧 Field tipBuild a “IMC 502 REQUIRED EXHAUST” schedule block in your template so every project has a one-glance list of special, hazmat, and HPM exhaust – even when the answer is “NONE.” It proves you actually ran the 502 checklist.Comment “IMC502-SUMMARY” if you want a paste-ready M-001 note and schedule sample template.