IMC 507 starts with one idea: the hood is a life safety system, not a "kitchen exhaust note." If it does not match the appliances, capture the effluent, and operate correctly, everything downstream breaks.
Plain English:
507.1 hood type rules
Commercial hoods must be Type I or Type II and designed to capture and confine cooking vapors and residues.
If ANY appliance under a single hood requires Type I, the whole hood must be Type I.
If Type II is required, you can install Type I or Type II.
507.1.1 operation and interlocks
Hoods must operate during cooking.
Exhaust rate must follow the hood listing OR the code sizing tables (Type I: 507.2.10, Type II: 507.3.4).
Type I fan must auto-start with appliance operation OR appliances must be interlocked so they cannot run unless exhaust is on.
Sensor-based start: fan must activate within 15 minutes of the first appliance being turned on.
Interlocks cannot extinguish standing pilots OR rely on the fire suppression system.
Multiple hoods on one exhaust (507.1.1.1)
If sensors are used and multiple hoods share one exhaust system, each hood needs its own sensor and be accessible from the hood outlet or a cleanout.
Domestic appliances used commercially (507.1.2): "Residential" appliances used for commercial purposes, provide Type I or II hoods per 507.2/507.3 (not IMC 505).
Fuel-burning conflicts (507.1.3): Draft-hood/atmospheric burner appliances are not allowed in the same space as a Type I or II hood unless in a sealed, self-closing enclosure with compliant combustion air.
507.1.4 + 507.1.5 practical design notes
Hood must be designed for thorough cleaning.
Hood outlets must optimize capture and each outlet serves max 12 ft of hood.
507.1.7 performance test + 507.1.7.1 capture test
Required after install and before final approval: verify exhaust airflow, makeup air per Section 508, and proper operation.
Capture and containment is verified visually with smoke/steam under real operating conditions (appliances hot, MUA on, space HVAC on).
On Plans: Why it matters
Common redlines: mixed-duty appliances under one hood without correct Type I call, missing interlock narrative, sensors shown without access, and no plan for performance testing.
Code Path: Where to show it
M-001: IMC 507.1 note with hood type logic, exhaust basis (listed or code), Type I interlock language, and testing requirements (507.1.7 and 507.1.7.1).
M-601 schedule: hood type, appliances served, exhaust basis, controls/interlock, design CFM, MUA CFM (508).
Check: Sequence and Controls
Drawings must show what triggers the Type I exhaust fan to start: appliance operation, demand-controlled sensor, or manual switch.
Controls sequence diagram must show exhaust fan ON -> makeup air ON -> gas valve interlock, and fire suppression activation -> fan shutoff + gas valve shutoff.
If sensor-based start, confirm each hood serving a shared exhaust system has its own accessible sensor per IMC 507.1.1.1.
Review Risk:
Missing or vague interlock narrative between hood exhaust, makeup air, and gas valve shutoff is the most common 507.1 plan review comment.
Sequences that rely on the fire suppression system to shut off standing gas pilots violate 507.1.1 - the interlock must not extinguish pilots through suppression activation.
Mixed-duty appliances under one hood not designated as Type I for the whole hood is a fast redline.
Field Tip:
Add an "IMC 507.1 CHECK" on the hood schedule: TYPE (I/II) + INTERLOCK (Y/N) + EXH BASIS (LISTED/CODE) + SENSOR PER HOOD (Y/N) + MUA (508) + PERF TEST (507.1.7).
Masterbuild QA Lens
Hood type selection (Type I vs Type II, per 507.1) drives the entire Ch5 compliance path. Confirm the hood type for each appliance is shown on M-601 with the appliance classification, BTU rating, and required capture velocity. Reviewers verify the hood type matches the cooking appliance before checking any other exhaust parameter.
Drawing / Submittal Check
For 507.1 (general requirements, operation, testing): the drawings must show the hood operation sequence - what triggers the hood to energize, what happens when the fire suppression system activates (fan and gas shutoff), and how the hood is tested after installation. The controls sequence diagram must show the interlock between the hood exhaust fan, makeup air, and the gas valve shutoff.
Common Review Risk
The most common 507.1 plan review
When To Escalate
Escalate when the hood control sequence involves a building management system, a fire alarm system, or a gas valve that was not designed by the mechanical engineer. Cross-discipline control interlocks for kitchen hoods require a controls sequence document that all involved disciplines - mechanical, electrical, controls, and fire protection - must review and sign off before construction.
Kitchen Exhaust Coordination
For kitchen exhaust, tie the hood schedule, appliance lineup, grease duct route, cleanouts, fan discharge, fire suppression interface, and make-up air strategy into one reviewable story.
Duct System Coordination
Commercial kitchen hood general requirements establish the exhaust duct connection, minimum airflow, and operational test protocol. The duct schedule should include design CFM, minimum CFM, and the basis for the listed hood.