210.0 H – — 2025 California Mechanical Code

Hangers. See Supports.

Hazardous Location. An area or space where combustible dust, ignitable fibers, flammable liquids, volatile liquids, gases, vapors, or mixtures are or may be present in the air in quantities sufficient to produce explosive or ignitable mix tures.

Hazardous Process Piping (HPP). A process material piping or tubing conveying a liquid or gas that has a degreeof-hazard rating in health, flammability, or reactivity of Class 3 or 4, as ranked by the fire code.

Health Facilities. [OSHPD 1, 1R, 2, 3, 4, 5 & 6] Build- ings specified within the statutory authority of the Depart- ment of Health Care Access and Information/Office of Statewide Hospital Planning and Development.

Heat Pump. A refrigeration system that extracts heat from one substance and transfers it to another portion of the same substance or to a second substance at a higher temperature.

Heat Recovery Ventilation (HRV) System. A device intended to remove air from buildings, replace it with outside air, and in the process transfer heat from the warmer to the colder airstreams.

Heating Degree Day. A unit, based upon temperature difference and time, used in estimating fuel consumption and specifying nominal annual heating load of a building. For any one day when the mean temperature is less than 65°F (18°C), there exist as many degree days as there is Fahrenheit degrees difference in temperature between mean temperature for the day and 65°F (18°C).

Heating Equipment. Includes warm air furnaces, warm air heaters, combustion products vents, heating air-distribution ducts and fans, and all steam and hot water piping, together with all control devices and accessories installed as part of, or in connection with, any environmental heating system or appliance regulated by this code.

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Heating System. A warm air heating plant consisting of a heat exchanger enclosed in a casing, from which the heated air is distributed through ducts to various rooms and areas. A heating system includes the outside air, return air, and supply air system, and all accessory apparatus and equipment installed in connection therewith.

High Limit Control Device. An operating device installed and serving as an integral component of a deep-fat fryer that provides secondary limitation of the grease temperature by automatically disconnecting the thermal energy input when the temperature limit is exceeded. [NFPA 96:3.3.32]

High Purity Piping. A form of process piping but is usually specified for critical clean applications in the semiconductor, pharmaceutical, biotechnology, chemical, fiber optics, food, and dairy industries.

Highside. The parts of a refrigeration system subjected to approximately condenser pressure.

Hood. An air-intake device connected to a mechanical exhaust system for collecting and removing grease-laden vapors, fumes, smoke, steam, heat, or odors from commercial food heat-processing equipment. Hood, Compensating. A hood for commercial food heat-processing equipment that has an outside-air supply with air delivered below or within the hood. Where makeup air is diffused directly into the exhaust within the hood cavity, it becomes a short-circuit hood.

Hood, Fixed Baffle. A listed unitary exhaust hood design where the grease removal device is a nonremovable assembly that contains an integral fire-activated water-wash fire-extinguishing system listed for this purpose. [NFPA 96-2014:3.3.33.1]

Hood, Type I. A kitchen hood for collecting and removing grease and smoke.

Hood, Type II. A general kitchen hood for collecting and removing steam, vapor, heat, or odors. HPM Storage Room. A room used for the storage or dispensing of hazardous production material (HPM) and that is classified as a Group H, Division 1, Division 2, Division 3, Division 4, or Division 5 Occupancy.

Hydronics. Of or relating to a heating or cooling system that transfers energy by circulating a fluid through a system of pipes or tubing. Hydronic System. Relating to, or being a system of, heating or cooling that involves the transfer of heat by circulating a fluid in a liquid state (such as water) or a gaseous state (such as steam).

Hydronic System, Ambient Temperature Loop (ATL). An endless closed loop system comprised of centralized pumping for the circulation of the contained fluid between multiple heat exchange devices installed on the loop.

Hydronic System, Closed-Loop. A hydronic system that uses a captive installed fluid mass that is circulated to transfer thermal energy between heat exchange sources and emitters installed on the system loop. Hydronic System, District Ambient Temperature Loop. An endless closed loop system comprised of centralized pumping for the circulation of the contained fluid between multiple heat exchange devices installed on the loop. The endless loop may run exterior to conditioned spaces in order to serve multiple structures and the heat exchange devices installed within.

Hydronic System, Fifth Generation (5G) System Configurations . An advanced ambient temperature (ATL) system that distributes near-ambient-temperature water among and between end-use buildings that are equipped with water-source heat pumps or other watersource HVAC equipment. Such systems stand in contrast to fourth generation (4G) systems that distribute hot water or chilled water to buildings to serve facility loads.

Hydronic System, Fourth Generation (4G) Sys- tem Configurations. A district geothermal energy system that distributes hot water and cold water for direct

use in the conditioned space.

Hydronic System, Geothermal Closed-Loop. A closed-loop hydronic geothermal system that uses one or more heat exchangers submerged in a body of water or buried in the ground, fluidly coupled to one or more heat exchangers or heat pumps serving one or more conditioned spaces or thermal storage vessels.

Hydronic System, Geothermal Open-Loop. An open-loop geothermal energy system draws in surface or ground water, passes it through one or more heat exchangers and/or heat pumps, and then discharges the water back into the environment.

Hydronic System, Non-Oxygen Barrier Closed- Loop. A hydronic system constructed all or in part with pipe or tubing that permit the diffusion of oxygen into the system fluid.

Hydronic System, Open-Loop. A hydronic system that takes in a fluid mass from an external source, transfers thermal energy into or out of the fluid by means of one or more heat exchangers, and then returns the fluid mass all or in part to the external source.

Hydronic System, Vented Closed-Loop. A hydronic system wherein the system volume is occupied in part by a gas, such as air. The gaseous content is vented so as to modulate or regulate the gas pressure and/or the system fluid pressure.