401.3 Filters — 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) § 401.3 · Effective January 1, 2026 · Official source: Building Standards Commission
[BSC-CG & DSA-SS] In mechanically ven- tilated buildings, provide regularly occupied areas of the building with air filtration media for outside and return air that provides at least a Minimum Efficiency Reporting Value (MERV) of 13. MERV 13 filters shall be installed prior to occupancy, and recommendations for maintenance with fil- ters of the same value shall be included in the operation and maintenance manual in compliance with Chapter 5, Division 5.5 of the California Green Building Standards Code (CAL- Green).
Exception: Existing mechanical equipment.
401.3.1 Labeling. Installed filters shall be clearly labeled by the manufacturer indicating the MERV rating.
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