/ Field knowledge · IMC 505 vs 507
A residential range used commercially is not IMC 505.
IMC 505 is domestic cooking exhaust. IMC 507 is commercial hoods. Domestic-looking equipment used commercially still has to meet Type I / Type II — it does not stay on 505 because the appliance looks residential.
Educational 2024 IMC 505 vs 507. Confirm occupancy, listing, and adopted FBC Mechanical edition. This is not a hood selection.
Stay on 505 when
- Residential-type cooking in Group R (and domestic-style equipment that still qualifies as residential-type in some non-R cases — occupancy decides).
- Listed equipment: UL 507 (hoods/downdrafts), UL 923 (OTR microwave), ANSI Z21.1 / UL 858 (range with integral downdraft). No unlisted field-built assemblies.
- Smooth rigid metal duct. No flex in the cooking exhaust path. No screen at termination. Outdoors unless 505.2 expressly permits a listed recirculating hood with charcoal filter — and Chapter 4 ventilation still has to exist.
- 505.4: if the domestic kitchen exhaust can exceed 400 cfm, makeup air at approximately the same rate, with a closure damper automatically interlocked with the hood. Draw path, damper, cfm, interlock.
- 505.5 multistory: shared riser in an IBC-rated shaft; rigid steel (min. 26-gage, SMACNA); backdraft dampers at each unit connection; dampers prohibited in the exhaust duct except as 505.3 allows.
- I-1 / I-2: IBC 420.9 path — DCT: minimum 500 cfm hood, room ventilation per 403.3.1, outdoor discharge. Ductless only if listed with charcoal filter.
Switch to 506 / 507 when
- The cooking load requires Type I or Type II classification. If ANY appliance under a hood requires Type I, the entire hood is Type I.
- Domestic appliances used commercially still meet Type I / Type II — not IMC 505.
- Then grease duct (506), hood geometry/airflow (507), makeup air (508), suppression, capture-and-containment test.
The 400 cfm decorative hood
Architect-specified domestic hoods often exceed 400 cfm. Missing MUA, damper, and interlock is the redline. Commercial cooking hidden as “just a residential range” is the next one.
Sources: 505 summary · 507 summary · commercial: 506–508 hub · tool: 505 vs 507.
What to send
Occupancy, menu or appliance list, hood cfm, and whether this is a dwelling, restaurant, or I-1/I-2. Cut sheets beat adjectives.
If it looks residential and cooks like a restaurant
Send occupancy and the appliance list. Masterbuild will say whether this is still 505 or already 507.
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.