/ Field knowledge · IMC 507.3
Type II is not “general exhaust.”
IMC 507.3: Type II is steam, heat, and combustion without grease. Calling it “general exhaust” is a first-cycle comment. Lock the appliance list before the permit — a griddle under a Type II hood is the expensive change.
Educational 2024 IMC 507.3. Confirm adopted edition. Distinct from the Type I path on commercial kitchen ventilation. If any appliance produces grease-laden vapors, Type I controls regardless of the hood label.
- 507.3: Type II hoods go over light-duty cooking, dishwashers, and heat/moisture appliances that do not produce grease/smoke. Also over appliances producing products of combustion without grease/smoke.
- Type I is allowed in place of Type II if it meets Type I installation rules. If a Type I hood serves ONLY dishwashers and Type II-only appliances, it does not need fire suppression or grease filters.
- 507.3.1 materials: steel min 0.0296 in (22 ga); stainless min 0.0220 in (24 ga); copper min 24 oz/sf; or other approved material/gage.
- 507.3.2 supports must handle hood load + unsupported ductwork + effluent + potential personnel load.
- 507.3.3 joints/seams/penetrations: follow Chapter 6; seal on the interior; smooth, readily cleanable, watertight.
- 507.3.4 capacity is NET exhaust = total exhaust minus any air supplied directly to the hood cavity.
- 507.3.4.1 light-duty minimums (cfm per linear ft): wall-mounted canopy 200; single island 400; eyebrow 250; double island 250 per side; backshelf/pass-over 250.
- 507.3.4.2 dishwasher: 100 cfm per linear ft of hood length.
Hood schedule columns from Daily Code Talk: appliance type (light-duty / DW) | NET cfm/lf | material/ga. If any appliance is changed to a grease-producing type after permit, upgrade to Type I before occupancy.
Steam kettle to griddle
The most common Type II inspection failure is an after-permit menu change. Confirm with the operator that appliance types are final before the set is filed. Missing NET cfm is a consistent plan-review flag.
Source: DCT 507.3 · ducts: 506.4 · Type I: 507.2 · makeup: makeup air.
What to send
The appliance list and whether anything produces grease-laden vapor.
If the menu is not locked
Send the appliance list. Masterbuild will say whether 507.3 even has a Type II path — or this is already a Type I grease-duct conversation.
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. NET cfm and gages below are 2024 IMC model-code education from Daily Code Talk — not a hood selection.