217.0 O – — 2025 California Mechanical Code
California Mechanical Code (Title 24, Part 4) · 2025 edition · updated 2026-10-19 · California
CBSC: official editions, supplements and errata
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) § 217.0 · Effective January 1, 2026 · Official source: Building Standards Commission
Occupancy. The purpose for which a building or part thereof is used or intended to be used.
Occupancy, Nontransient. Occupancy of a dwelling unit or sleeping unit for more than 30 days. [ASHRAE 62.1:3]
Occupancy Classification. Classifications are defined in the building code. [HCD 1, HCD 2 & SFM] Whenever the term “Building Code” is used in this code, it shall mean the California Building Code, Title 24, Part 2.
Occupational Exposure Limit (OEL). The timeweighted average (TWA) concentration for a normal 8-hour workday and a 40-hour workweek to which nearly all workers can be repeatedly exposed without adverse effect, based on the OSHA PEL, ACGIH TLV-TWA, TERA OARSWEEL, or consistent value. [ASHRAE 34:3]
Occupiable Space. An enclosed space intended for human activities, excluding spaces that are intended to be occupied occasionally and for short periods of time, such as storage rooms, equipment rooms, and emergency exitways. [ASHRAE 62.1:3]
Open Combustible Construction. Combustible building construction, including wall, structural framing, roof, roof ceiling, floor, and floor-ceiling assemblies, adjacent to a grease duct on three or fewer sides where one or more sides require protection in accordance with Section 507.4.
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