405.3 Bathroom Exhaust — 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) § 405.3 · Effective January 1, 2026 · Official source: Building Standards Commission
A mechanical exhaust directly to the outdoors shall be provided in each room containing a bathtub, shower, or tub/shower combination. The fan shall run intermittently (on demand) or continuously. A readily accessible manual control designed to be operated as needed or an automatic control shall be provided for intermittent operations. [HCD 1 & HCD 2] Each bathroom shall also be mechanically ventilated in accordance with Division 4.5 of the California Green Building Standards Code (CALGreen).
405.3.1 Exhaust Rate. The exhaust rate shall be not less than 50 ft [3] /min (23.6 L/s) for intermittent operation and 25 ft [3] /min (11.8 L/s) for continuous operation.
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