Kitchen exhaust > 400 cfm requires makeup air with damper (auto-opens with exhaust); gas-burning trigger
2025 RCNYS §M1503.6 Makeup air for high-rate exhausts (>400 cfm)Description
When a gas, liquid, or solid-fuel-burning appliance that isn't direct-vent or mechanical-draft is located within a dwelling's air barrier, AND any single exhaust system can move more than 400 cfm, makeup air at approximately the exhaust rate must be supplied — through at least one outdoor air duct with a damper that opens automatically when the exhaust runs. Exception: space-cooling exhausts intended only when windows are open.
Why this exists
Pro-grade range hoods (1000+ cfm) without makeup air create dangerous negative pressure that backdrafts gas water-heater fumes (CO!) into the dwelling. Architects specifying high-cfm hoods MUST also spec a makeup-air system; this is a non-negotiable life-safety detail.
Measurements
| Property | Operator | Value | Unit | Note |
|---|---|---|---|---|
makeupTrigger | min | 400 | cfm | Exhaust rate triggering makeup-air requirement |
Categories
Applies to
- Jurisdiction: New York State
Source
Solver enforcement
Browsable only — the solver does not currently enforce this directive (no spec-level data to check against). This entry exists so the architect personas can cite it in conversation and the user can read what the rule says.
Related directives
- Garage / dwelling fire separation · IRC R302.6
- Natural light in habitable rooms · IRC R303.1
- Habitable space minimum ceiling height · IRC R305.1
- Egress window net opening dimensions · IRC R310.2
- Stair riser, tread, and headroom · IRC R311.7
Last reviewed 2026-05-15.