Daily Code Talk — IMC 505 (Domestic Cooking Exhaust): Mini-Series Kickoff

Domestic kitchen exhaust looks simple until you have big hoods, tight envelopes, or multistory shafts. IMC 505 is where “just a range hood” becomes a real exhaust system with listings, duct rules, and makeup air.We’ll cover 505 in three parts:• Part 1 (505.1–505.3): Equipment, listings, and ductsHow domestic cooking exhaust equipment is listed (UL 507, UL 858, UL 923, ANSI Z21.1), when ductless hoods are allowed, what duct materials are permitted, smooth airtight ducts with backdraft dampers, and the special case where downdraft systems can use PVC under a slab.• Part 2 (505.4–505.5): Makeup air and common multistory systemsWhen makeup air is required for hoods over 400 cfm and how it must be interlocked. Common domestic kitchen exhaust shafts in multistory buildings: fire-rated shaft, straight 26-gauge rigid duct, fan outside the airstream on standby power, no dampers or screens, cleanout at the base, and the shaft serving only kitchen exhaust.• Part 3 (505.6–505.8): Other than Group R, Group I-1 and I-2When “domestic” cooking used in non-residential occupancies still needs domestic exhaust systems, plus the 500 cfm minimum hood rate in I-1 and I-2, outdoor discharge, and the limited ductless hood exception with charcoal filters.🏗️ Why it mattersCommon plan-review hits: calling something “domestic” but routing it like a commercial hood, no makeup air on big island hoods, common shafts drawn with offsets or dampers, and I-1/I-2 kitchens using undersized or recirculating hoods that do not meet the 500 cfm and discharge requirements.🗺️ Where to show it• M-001: “IMC 505 DOMESTIC COOKING EXHAUST” note listed equipment, ducts to outdoors (or listed ductless), makeup air for hoods >400 cfm, and rules for any common multistory shaft.• M-101: Range hood locations, duct routing, duct type callouts, and termination locations.• M-601: Simple hood / domestic kitchen exhaust schedule with HOOD CFM, DUCT SIZE/MATERIAL, MAKEUP AIR (Y/N), COMMON SHAFT (Y/N), and CODE REF (505.x).✅ Do• Coordinate hood cfm, duct path, and makeup air with the architect and structural so the route, shaft, and openings are all realistic.⛔ Don’t• Treat large domestic hoods or multistory shafts as “just another exhaust line.”🔧 Field tipAdd a “DOMESTIC KITCHEN EXHAUST – IMC 505 CHECK” box in your template: equipment type/listing, hood cfm, duct route and termination, makeup air needed (Y/N), common shaft (Y/N), Group R vs I-1/I-2. If every line is filled before you issue, you’ve already answered most reviewer questions.Comment “IMC505” if you want a paste-ready domestic kitchen exhaust checklist and starter schedule line for M-001 and M-601.