407.5 Variable Air Volume — 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) § 407.5 · Effective January 1, 2026 · Official source: Building Standards Commission
407.5.1 Variable Air Volume Systems (VAV). Variable air volume systems subjecting the patient to a fluctuating air movement are not acceptable for airborne infection isolation rooms, protective environment rooms or those critically sensitive areas listed in Section 322.0. For non- sensitive areas, variable air volume systems meeting the following criteria can be considered:
407.5.1.1 The VAV system shall comply with code requirements for outside air, total air, and pressure relationship through the full range of operation from
minimum to maximum.
407.5.1.2 The central return or exhaust fan shall be controlled to accomplish the variable air volume requirements of the individual rooms served by the fan as described in Section 407.5.1.3.
407.5.1.3 Spaces with pressure requirements per Table 4-A shall utilize an automatic modulating damper in the return or exhaust air for each space. The damper will modulate from full open to minimum position in conjunction with the supply air VAV ter- minal equipment to maintain space pressurization.
407.5.1.4 Sensitive areas or rooms shall be provided with controls on the return or exhaust duct system to maintain constant air flows.
407.5.1.5 Return air controls shall be provided for each system, floor or area with similar conditions.
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