605.3 [OSHPD 1, 2, 4 & 5] — 2025 California Mechanical Code
California Mechanical Code (Title 24, Part 4) · 2025 edition · updated 2026-09-25 · 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) § 605.3 · Effective January 1, 2026 · Official source: Building Standards Commission
Thermal or acoustical lining materials shall not be installed within ducts which are down- stream of the 99.97 percent high-efficiency particulate air (HEPA) filter required in Section 408.2.1 for protective envi-
ronment rooms.
DUCT SYSTEMS
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