606.4 Combination Fire/Smoke Dampers — 2025 California Mechanical Code
California Mechanical Code (Title 24, Part 4) · 2025 edition · updated 2026-09-25 · California
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Italicized text is a California amendment to the model code, as printed in the official publication.
Cite as: 2025 California Mechanical Code (Title 24, Part 4) § 606.4 · Effective January 1, 2026 · Official source: Building Standards Commission
Combination fire/smoke dampers shall comply with UL 555 and UL 555S and the requirements in Section 606.1 and Section 606.2.
606.4.1 When the automatic activation of a smoke damper or a combination smoke-fire damper occurs, the HVAC system serving such dampers shall immediately shut down.
Exceptions:
(1) HVAC systems that are part of an engineered smoke evacuation system.
(2) Where the automatic activation causes all the smoke dampers and combination smoke-fire dampers to close in the enclosed space having a common atmos- phere where openings are required to be protected.
(3) Where analysis demonstrates shutoff would create a greater hazard.
The HVAC system shall not be restarted again until all the dampers are reset and fully opened.
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