222.0 T – — 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) § 222.0 · Effective January 1, 2026 · Official source: Building Standards Commission
Termination, Duct. The final or intended end portion of a duct system that is designed and functions to fulfill the obligations of the system in a satisfactory manner. [NFPA 96:3.3.19]
Testing Agency. [HCD 1 & HCD 2] See “Approved Test- ing Agency.”
Thermal Highway. A collection one or more GeoMicroDistricts that acts as an energy transport system and supplies or accepts energy from multiple GeoMicroDistricts, individual buildings, or other sources. Also known as convective circulation circuit.
Thermal Recovery Unit. A device or series of devices whose purpose is to reclaim only the heat content of air, vapors, gases, or fluids that are being expelled through the exhaust system and to transfer the thermal energy so reclaimed to a location whereby a useful purpose can be served. [NFPA 96:3.3.49]
Thermal Resources. A source for a heating and a sink for a cooling. There are two types of sources:
(1) Conventional-type: such systems are known as geothermal energy systems, such as air-source resources and ground-source resources.
(2) Opportunistic-type: such systems use water-source resources (e.g., oceans, rivers, raw sewage pipes, treated sewage outfall, potable water pipes, etc.), process byproduct heat resources (e.g., data center cooling process reject heat, industrial process reject heat, etc.), and other resources.
Thermosiphon. The natural circulation of fluids due to temperature differential.
Trained. A person who has become proficient in performing a skill reliably and safely through instruction and practice/field experience acceptable to the Authority Having Jurisdiction. [NFPA 96:3.3.50]
Transition Gas Riser. A listed or approved section or sections of pipe and fittings used to convey fuel gas and installed in a gas piping system for the purpose of providing a transition from belowground to aboveground.
Trap. A cuplike or U-shaped configuration located on the inside of a duct system component where liquids can accumulate. [NFPA 96:3.3.51]
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