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California Mechanical Code (Title 24, Part 4) · 2025 edition · updated 2026-10-23 · 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) · Effective January 1, 2026 · Official source: Building Standards Commission
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OCCUPATION CLASSIFICATION
Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217.0
ODOROUS ROOMS . . . . . . . . . . . . . . . . . . . . . . . . . . . 413.0
OIL BURNING BOILERS . . . . . . . . . . . . . (see Boiler types,
oil burning)
OPEN TOP BROILER UNIT . . . . . . . . . . . . . . . . . . . . . 921.0
OPENINGS
Air heaters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 914.7
Attics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . E 502.11
Ducts. . . . . . . . . . . . . . . . . . . . . . . 506.6, 510.1.4, 510.3
Exhaust and intake . . . . . . . . . . . . . . . . . 305.3.2, 925.4
For access . . . . . . . . . . . . . . . . . . . . . . . 506.3, 510.1.4,
514.1.2, 1406.2.1.4
For combustion air. . . . . . . . . . . . . . . . . . 701.6, C 109.1
Furnaces. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 906.9
Illuminating appliances . . . . . . . . . . . . . . . . . . . . . 923.4
Ratproofing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 316.10
Relief. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 914.7
Screens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 802.1.2
Ventilation . . . . . . . . . . . 402.2.1.2, 402.2.1.3, 402.2.1.4,
402.2.1.5, 402.2.1.1, 402.2.1.6,
402.2.3, 802.1.2, 802.10.3,
1105.5.1, 1106.3, E 605.1.1
OSHPD 1R . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301.7
OUTDOOR AIR INTAKES and EXHAUST OUTLETS . . 407.2
Building Pressurization . . . . . . . . . . . . . . . . . . . . . 407.8
Hazardous Exhaust Outlets. . . . . . . . . . . . . . . 407.2.2.1
OUTDOOR AIR RATE
Calculation. . . . . . . . . . . . . . . . . . . . . . . . . . Appendix H
OUTLETS
Appliance flue . . . . . . . . . . . . . . . . . . . . 203.0, 802.10.5
Draft hood . . . . . . . . . . . . 802.10.2.1, 802.10.5, 803.1.1
Exhaust. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 508.7
Fuel gas piping . . . . . . . . . . . . 1305.2, 1306.3, 1310.10,
1312.8, 1314.4
OVER PRESSURE PROTECTION
Fuel gas piping . . . . . . . . . . . . . . . . . 1308.6.1, 1310.6.1
OVERHEAD HEATERS
In garages. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 925.5
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