/ Field knowledge · IMC 507.2
“Type I” on the schedule is not the hood.
Type I hoods are required where appliances produce grease or smoke — generally medium-, heavy-, and extra-heavy-duty cooking. Labeling “Type I” on a schedule is not the hood. The drawings have to show the listed exhaust rate, materials, liquid-tight construction, 18-inch combustible clearance (or a listed reduction), and how any hood portion that penetrates a ceiling is enclosed. Field-applied grease-duct wrap cannot satisfy that enclosure.
Educational 2024 International Mechanical Code (IMC) 507.2–507.2.7 from Daily Code Talk. Confirm the adopted edition. Distinct from Type II (507.3), makeup air (508), and the kitchen overview. This is not a hood selection.
- 507.2.1: Type I hoods labeled with the minimum exhaust flow rate (cfm per linear foot) for capture and containment based on duty classification.
- 507.2.2: Type I hoods serving extra-heavy-duty appliances cannot cover heavy-, medium-, or light-duty appliances, and must discharge to an exhaust system independent of other exhaust systems.
- 507.2.3 materials: steel 18 gage minimum (0.0466 in) or stainless 20 MSG minimum (0.0335 in).
- 507.2.4: noncombustible supports, designed for hood load plus unsupported grease-duct load, effluent loading, and potential personnel loads.
- 507.2.5: exterior joints, seams, and penetrations — continuous external liquid-tight weld or braze to the lowest outermost perimeter. Interior seams sealed grease-tight (exceptions for listed sealing devices and smooth internal welds).
- 507.2.6: default 18 in clearance to combustibles. Exceptions include noncombustible wallboard protection and UL 710 listed hoods with reduced clearances (follow the listing).
- 507.2.7: hood portions penetrating ceilings, walls, or furred spaces must comply with 506.3.11 enclosure. Field-applied grease-duct wrap systems (506.3.11.2) cannot be used to satisfy this specific requirement.
Typical redlines: “Type I” with no hood listing or cfm/ft, missing liquid-tight notes, 18 in clearance conflicts, and ceiling penetrations drawn with no enclosure strategy.
Extra-heavy-duty fryers under a hood that also covers a light-duty steam table
Or wrap used to “enclose” a hood that punches the ceiling. 507.2.2 and 507.2.7 fail before the fan is even selected.
Source: Daily Code Talk — IMC 507.2 · exceptions: 507.1 listings · interlock: 507.1.1 · geometry: 507.1.6 · filters: 507.2.8–507.2.11 · Type II: 507.3 · makeup: 508 · shafts: no damper in grease shafts.
What to send
The cooking lineup (duty class), the hood catalog / listing, whether the hood penetrates a ceiling, and the grease-duct enclosure method.
If the hood is labeled Type I and the listing is missing
Send the menu and the cut sheet. Masterbuild will say whether 507.2 still has no cfm/ft — or 507.2.7 still has wrap used as enclosure.
Send Project Background+1 (786) 398-6940 · osmany.portal@masterbuildconsulting.com
Masterbuild provides engineering services under a written scope. Nothing on this page is project-specific engineering advice, a code interpretation for your project, or a representation about permit approval. Confirm the adopted edition. 18 gage / 20 MSG, 18 in clearance, extra-heavy-duty independence, and the wrap prohibition at 507.2.7 are 2024 IMC 507.2 education from Daily Code Talk — not a hood design. This page is not legal advice.