Plain English:
507.1 hood type rules
Commercial hoods must be Type I or Type II.
They must capture and confine cooking vapors and residues.
If ANY appliance under one hood requires Type I, the entire hood must be Type I.
If Type II is required, you may install Type II OR Type I (Type I is always the "safe upgrade," but it triggers Type I installation rules when applicable).
507.1 key exceptions and "no hood required" cases (where listed/approved)
A lot of plan review pain comes from missing the listings.
1. Listed recirculating systems (UL 710B)
If the kitchen uses a factory-built recirculating system listed/labeled to UL 710B (installed per IMC 304.1), several IMC 507 hood rules don't apply (ex: hood outlet placement, hood size/location rules, certain Type I construction/filter/airflow provisions, and Type II hood material rules).
The space is still treated as a kitchen and must be ventilated per Table 403.3.1.1.
For ventilation floor area calc: each appliance counts as at least 100 sf.
2. No hood required (specific cases)
A hood is not required at/above:
UL 710B listed recirculating systems (again).
Listed integral downdraft systems (listed for the application per NFPA 96).
Smoker ovens with integral exhaust listed/tested for the application.
UL 2162 listed wood-fuel ovens (vented per manufacturer).
UL 197 listed electric cooking appliances for reduced grease emissions.
UL 921 listed electric dishwashers with self-contained condensing.
Certain "heat/moisture only" appliances when the HVAC/separate removal system accounts for the load: Provide space exhaust at 0.70 cfm/sf, and for floor area calcs count each non-Type-II appliance as at least 100 sf (plus that extra area exhausted at 0.70 cfm/sf).
On Plans: Why it matters
Common redlines: "recirc hood" shown with no UL 710B listing, downdraft called out with no listing basis, and designers skipping hood exhaust but also skipping the required space exhaust/ventilation logic.
Code Path: Where to show it
M-001: "IMC 507 HOOD TYPE BASIS" note + a dedicated "EXCEPTIONS" note listing UL 710B / UL 197 / UL 921 / UL 2162 / NFPA 96 downdraft (as applicable).
Hood/appliance schedule: include LISTING STANDARD + MODEL for any exception-driven design.
Ventilation schedule noting Kitchen spaces: when using the heat/moisture-only option, show the 0.70 cfm/sf and the "100 sf minimum per appliance" basis.
Check: Exception Documentation
M-001 must include a dedicated IMC 507 EXCEPTIONS note listing the specific exception number, the listing standard (UL 710B / UL 197 / UL 921 / UL 2162 / NFPA 96), and the model number.
Hood and appliance schedule must include the listing standard and model number for every exception-driven design decision.
For the heat/moisture-only appliance path, show 0.70 cfm/sf and the 100 sf per appliance minimum on the ventilation schedule.
Review Risk:
Exception claims not pre-coordinated with the AHJ frequently generate plan review comments - contact the AHJ before issuing the permit set when relying on a 507.1 exception.
Undocumented exceptions (no exception number, no listing standard, no basis on the drawings) are the most common 507.1 comment.
A recirc hood shown on plans without a UL 710B listing standard and model number on the schedule will be rejected.
Field Tip:
Run a quick "LISTING CHECK" on every kitchen plan:
If you're claiming an exception, put the UL/NFPA standard + model number on the drawings. If it's not on the sheet, it's not defensible.
Masterbuild QA Lens
Hood listing and the fire suppression system are not independent - the suppression system must be listed for the specific hood model and cooking equipment. Confirm the suppression system manufacturer and the hood manufacturer have issued a joint listing or an engineer-of-record approval for the combination. A suppression system that is not listed for the hood is an immediate life-safety concern.
Drawing / Submittal Check
For 507.1 general requirements and exceptions: the drawings must specifically address any exception being claimed (hood over a listed appliance, reduced exhaust rate per listed hood performance). Exceptions under IMC 507.1 must be documented on M-001 with the specific exception number and the basis for the exception. Undocumented exceptions are a common source of comments.
Common Review Risk
Exception claims under 507.1 that were not pre-coordinated with the AHJ frequently generate plan review comments requesting justification. Write the exception claim specifically: IMC 507.1 exception [number]: appliance is listed to [standard], hood is listed to [standard], and the listing permits the claimed reduction. A vague exception note - hood not required per exception - without a specific basis will generate a plan review
When To Escalate
Escalate when the project relies on a 507.1 exception that the local AHJ has not accepted before. Code exceptions that are accepted in one jurisdiction are not automatically accepted in another. Confirm the AHJ's position on the specific exception before the permit is filed - an exception that is denied during plan review requires a design change that may affect the kitchen layout.
Load Assumption Check
Section 507 Part 6 covers hood testing and performance verification. The test condition must match the design load - confirm the design exhaust CFM, capture velocity, and makeup air volume are achievable at the conditions that will exist during the operational test.
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.