Refs: IMC 304.1–304.4; IMC 202; IECC; NFPA 30A; IBC (hazard/guards for context).
🧠 Plain English Highlights
304.1 General: Install per approval + listing + manufacturer’s instructions (MI) + IMC. Keep MI on site for inspection.
304.2 Conflicts: If code vs listing/MI conflict, IMC governs—except when IMC is less restrictive; then follow listing/MI.
304.3 Ignition source elevation: In public/private/repair garages, fuel-dispensing facilities, hazardous locations → ignition source ≥18 in above floor. Rooms that open directly to a private garage are part of the garage. Exception: FVIR-listed appliances (flammable-vapor ignition resistant) need no elevation.
304.3.1 Parking garages: Rooms with fuel-fired appliances connecting to a parking garage need a two-door vestibule; one door allowed if ignition source is elevated per 304.3. Exception: installs meeting 304.6.
304.4 Prohibited locations: No ignition-source equipment/appliances in Group H or control areas with open use/handling/dispensing of flammables/explosives.
🏗️ Why It MattersTop redlines: MI not on site, wrong choice between IMC vs MI when they conflict, ignition sources too low in garages/adjacent rooms, missing vestibule separation, and placing ignition sources in Group H areas.
🧾 Where To Show It (sheet map)
M-001: “Install per listing + MI + IMC; MI on site. Conflicts per 304.2. Ignition sources ≥18 in where required. Vestibule per 304.3.1 when a room with fuel-fired appliances opens to a parking garage. No ignition-source installs in Group H open-use areas.”
M-101/…: Flag garage-adjacent rooms, show vestibule (two doors or elevation basis), annotate 18-in elevation or FVIR listing, and note hazard areas as “no ignition source.”
M-501/502: Typical garage vestibule detail; elevated platform detail with dimensions; FVIR notation example.
M-601: Columns for Ignition Source Height (in), FVIR (Y/N), Vestibule (Y/N/NA), Location Type.
🔧 Quick Field Tip
If the room communicates with a private garage, treat it as garage for 304.3.
For WH/furnace in or next to a garage: choose FVIR or provide 18-in elevation; add vestibule where 304.3.1 triggers.
When MI is stricter than IMC, follow MI; when MI is looser, follow IMC. Note the MI page on the schedule.
Comment “304 KIT” for a 1-page Part-1 install check card (notes, details, schedule fields).DM “ADVISORY” for a rapid plan-review sweep.