203.0 – A –

Absorption Unit. An absorption refrigeration system that has been factory-assembled and tested prior to its installation.

Accepted Engineering Practice. That which conforms to technical or scientific-based principles, test, or standards that are accepted by the engineering profession.

Access Panel. A closure device used to cover an opening into a duct, an enclosure, equipment, or an appurtenance.

[NFPA 96:3.3.1]

Accessible. Where applied to a device, appliance, or equipment, “accessible” means having access thereto, but which first may require the removal of an access panel, door, or similar obstruction.

Accessible, Readily. Having a direct access without the necessity of removing a panel, door, or similar obstruction.

Accessory Dwelling Unit. [HCD 1 & HCD 2] An attached or detached residential dwelling unit that provides complete independent living facilities for one or more persons and is located on a lot with a proposed or existing primary residence. Accessory dwelling units shall include permanent provisions for living, sleeping, eating, cooking, and sanitation on the same parcel as the single-family or multifamily dwelling is or will be situated. (See Government Code Section 65852.2.)

Air, Class 1. Air with low contaminant concentration, low sensory-irritation intensity, and inoffensive odor. [ASHRAE 62.1:5.18.1]

Air, Class 2. Air with moderate contaminant concentration, mild sensory-irritation intensity, or mildly offensive odors. Class 2 air also includes air that is not necessarily harmful or objectionable, but that is inappropriate for transfer or recirculation to spaces used for different purposes. [ASHRAE 62.1:5.18.1]

Air, Class 3. Air with significant contaminant concentration, significant sensory-irritation intensity, or offensive odor.

[ASHRAE 62.1:5.18.1]

Air, Class 4. Air with highly objectionable fumes or gases or with potentially dangerous particles, bioaerosols, or gases, at concentrations high enough to be considered as harmful.

[ASHRAE 62.1:5.18.1]

Air, Combustion. See Combustion Air.

Air, Conditioned. Air that has been treated to achieve a desired level of temperature, humidity, or cleanliness.

Air, Dilution. Air that enters a draft hood or draft regulator and mixes with the flue gases. [NFPA 54:3.3.2.2]

Air, Exhaust. Air being removed from any space or piece of equipment and conveyed directly to the atmosphere by means of openings or ducts.

Air, Makeup. Air that is provided to replace air being exhausted.

Air, Outside. Air from outside the building intentionally conveyed by openings or ducts to rooms or to conditioning equipment.

Air, Relief. [OSHPD 1, 2, 3, 4 & 5] Air being exhausted directly from a building or a return duct system which is not contaminated by odors or other contaminants and could oth- erwise be used as return air if not exhausted from the building.

Air, Recirculated. Air that is removed from a conditioned space or zone and reused as supply air.

Air, Return. Air from the conditioned space or zone that is returned through ducts or plenums to the conditioning equipment for reconditioning.

Air, Supply. Air being conveyed to a conditioned space or zone through ducts or plenums from a heat exchanger of a heating, cooling, absorption, or evaporative cooling system.

Air, Transfer. Air that is relocated from one conditioned space or zone to another space through ducts, plenums, or transfer grills.

Air Dispersion Systems. Materials intended for use in air handling systems in exposed locations operating under positive pressure.

Air Exfiltration. Leakage of air from a conditioned space(s) to an unconditioned space(s) or to the outdoors through openings in the building envelope, often attributable to wind pressure, stack pressure, or positive pressurization of the building. Also known as air leakage.

Air-Handling Unit. A blower or fan used for the purpose of distributing supply air to a room, space, zone, or area.

Air Infiltration. Leakage of outdoor air or air from an unconditioned space(s) into a conditioned space(s) through openings in the building envelope, often attributable to wind pressure, stack pressure, or negative pressurization of the building. Also known as air leakage.

Air Intakes. An opening in a building’s envelope whose purpose is to allow outside air to be drawn into the structure to

DEFINITIONS

contained fuel supply and is not secured or attached to a building by any means other than by a factory-installed power supply cord.

Appliance, Vented. An appliance designed and installed in such a manner that all products of combustion are conveyed directly from the appliance to the outdoor atmosphere through an approved chimney or vent system. Appliance Categorized Vent Diameter/Area. The minimum vent diameter/area permissible for Category I appliances to maintain a nonpositive vent static pressure when tested in accordance with nationally recognized standards.

[NFPA 54:3.3.5]

Appliance Flue Outlet. The opening or openings in a cooking device where vapors, combustion gases, or both leave the cooking device. [NFPA 96:3.3.4] There might or might not be ductwork attached to this opening. Appliance Fuel Connector. An assembly of listed semirigid or flexible tubing and fittings to carry fuel between a fuel-piping outlet and a fuel-burning appliance.

Approved. Acceptable to the Authority Having Jurisdiction.

Exception: [HCD 1 & HCD 2] “Approved” means meeting the approval of the Enforcing Agency, except as otherwise provided by law, when used in connection with any system, material, type of construction, fixture or appliance as the result of investigations and tests conducted by the agency, or by reason of accepted principles or tests by national author- ities, or technical, health, or scientific organizations or agen- cies.

Notes :

(1) See Health and Safety Code Section 17920 for “Approved” as applied to residential construction and buildings or structures accessory thereto, as referenced in Sections 1.8.2.1.1 and 1.8.2.1.2.

(2) See Health and Safety Code Section 17921.1 for “A pproved” as applied to the use of hotplates in resi- dential construction referenced in Sections 1.8.2.1.1 and 1.8.2.1.2.

(3) See Health and Safety Code Section 19966 for “Approved” as applied to Factory-Built Housing as ref- erenced in Sections 1.8.2.1.1 and 1.8.2.1.2.

(4) See Health and Safety Code Section 18201 for “Approved” as applied to Mobilehome Parks as refer- enced in Section 1.8.2.1.3.

(5) See Health and Safety Code Section 18862.1 for “Approved” as applied to Special Occupancy Parks as referenced in Section 1.8.2.1.3.

Approved Testing Agency. An organization primarily established for purposes of testing to approved standards and approved by the Authority Having Jurisdiction. approved by the Authority Having Jurisdiction. [HCD 1 & HCD 2] “Approved Testing Agency” is any agency which is deter- mined by the Enforcing Agency, except as otherwise provided by statute, to have adequate personnel and expertise to carry out the testing of systems, materials, and various types of con- struction, fixtures or appliances.

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replace inside air that is removed by exhaust systems or to improve the quality of the inside air by providing a source of air having a lower concentration of odors, suspended particles, or heating content. [NFPA 96:3.3.2] Air-Moving System. A system designed to provide heating, cooling, or ventilation in which one or more air-handling units are used to supply air to a common space or are drawing air from a common plenum or space. Air Pollution Control Devices. Equipment and devices used for the purpose of cleaning air passing through them or by them in such a manner as to reduce or remove the impurities contained therein. [NFPA 96:3.3.3]

Air Terminal Device. [OSHPD 1, 2, 3, 4 & 5] Any device (e.g., grille, register, diffuser) placed in an opening to a room, through which controlled air enters or leaves. Com- ponent of the air-distribution system which has the purpose of achieving the predetermined movement of air into or from a treated space.

Anchors. See Supports.

Anodeless Riser. An assembly of steel-cased plastic pipe used to make the transition between plastic piping installed underground and metallic piping installed aboveground.

[NFPA 54:3.3.3]

Appliance. A device that utilizes fuel or electricity as an energy source to produce light, heat, power, refrigeration, or air conditioning. This definition also includes vented decorative appliances and electric storage or tankless water heaters.

Appliance, Closed Combustion Solid-Fuel-Burn- ing. A heat-producing appliance that employs a combustion chamber that has no openings other than the flue collar, fuel-charging door, and adjustable openings provided to control the amount of combustion air that enters

the combustion chamber.

Appliance, Direct Vent. Appliances that are constructed and installed so that all air for combustion is derived directly from the outdoors and all flue gases are discharged to the outdoors. [NFPA 54:3.3.4.2]

Appliance, Electric Heating. A device that produces heat energy to create a warm environment by the application of electric power to resistance elements, refrigerant compressors, or dissimilar material junctions. Appliance, Fan-Assisted Combustion System. An appliance equipped with an integral mechanical means to either draw or force products of combustion through the combustion chamber or heat exchanger.

[NFPA 54:3.3.95.2]

Appliance, Low-Heat. A fuel-burning appliance that produces a continuous flue gas temperature, at the point of entrance to the flue, of not more than 1000°F (538°C).

Appliance, Medium-Heat. A fuel-burning appliance that produces a continuous flue gas temperature, at the point of entrance to the flue, of more than 1000°F (538°C) and less than 2000°F (1093°C).

Appliance, Portable Heating. A heating appliance designed for environmental heating that may have a self

32 2025 CALIFORNIA MECHANICAL CODE

DEFINITIONS

200 000 Btu/h (58.6 kW), or an operating temperature exceeding 210°F (99°C) that provides hot water to be used externally to itself.

Boiler, Low-Pressure Hot-Water-Heating. A boiler furnishing hot water at pressures not exceeding 160 psig (1103 kPa) and at temperatures not exceeding 250°F (121°C).

Boiler, Low-Pressure Steam-Heating. A boiler furnishing steam at pressures not exceeding 15 psig (103 kPa).

Boiler, Miniature. A power boiler having an internal shell diameter of 16 inches (406 mm) or less, a gross volume of 5 cubic feet (0.14 m [3] ) or less, a heating surface of 20 square feet (1.86 m [2] ) or less (not applicable to electric boilers), and not exceeding 100 psig (689 kPa).

Boiler, Package. A class of boiler defined herein and shall be a boiler equipped and shipped complete with fuel-burning equipment, automatic controls and accessories, and mechanical draft equipment.

Boiler, Power. A boiler in which steam is generated at pressures exceeding 15 psig (103 kPa).

Boiler, Power Hot Water (High Temperature Water Boiler). A boiler used for heating water or liquid to a pressure exceeding 160 psig (1103 kPa) or to a temperature exceeding 250°F (121°C).

Boiler, Steam-Heating. A boiler operated at pressures not exceeding 15 psig (103 kPa) for steam.

Boiler, Water Heater or Hot-Water-Heating. An appliance designed primarily to supply hot water for domestic or commercial purposes and equipped with automatic controls limiting water temperature to a maximum of 210°F (99°C).

Boiler Room. A room where boilers are installed.

Bonding Conductor or Jumper. A reliable conductor to ensure the required electrical conductivity between metal parts required to be electrically connected. [NFPA 70:100(I)]

Borehole. A vertical or horizontal shaft typically cored, drilled or bored into the earth for geothermal system installations.

Breathing Zone. The region within an occupiable space between planes 3 inches and 72 inches (76 mm and 1829 mm) above the floor and exceeds 2 feet (610 mm) from the walls or fixed air-conditioning equipment. [ASHRAE 62.1:3]

Breathing Zone Outdoor Airflow. The outdoor airflow required in the breathing zone of the occupiable space or spaces in a ventilation zone.

Breeching. A metal connector for medium- and high-heat appliances.

Broiler. A general term including broilers, salamanders, barbecues, and other devices cooking primarily by radiated heat, excepting toasters. [NFPA 54:3.3.14]

BTU/H. The listed maximum capacity of any appliance, absorption unit, or burner expressed in British thermal units input per hour, unless otherwise noted.

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Appurtenance. An accessory or a subordinate part that enables the primary device to perform or improves its intended function. [NFPA 96:3.3.5]

Assembly Building. A building or a portion of a building used for the gathering together of 50 or more persons for such purposes as deliberation, education, instruction, worship, entertainment, amusement, drinking, dining, or awaiting transportation. [HCD 1, HCD 2 & SFM] Refer to the Cali- fornia Building Code, Title 24, Part 2 for use and occupancy classification.

Authority Having Jurisdiction. The organization, office, or individual responsible for enforcing the requirements of a code or standard, or for approving equipment, materials, installations, or procedures. The Authority Having Jurisdiction shall be a federal, state, local, or other regional department or an individual such as a plumbing official, mechanical official, labor department official, health department official, building official, or others having statutory authority. In the absence of statutory authority, the Authority Having Jurisdiction may be some other responsible party. This definition shall include the Authority Having Jurisdiction’s duly authorized representative. [HCD 1, HCD 2, OSHPD 1, 1R, 2, 3, 4, 5, 6 & SFM] “Authority Having Jurisdiction” shall mean “Enforcing Agency” as defined in Section 207.0 of this code.

Automatic. That which provides a function without the necessity of human intervention.

Azeotrope. A refrigerant blend containing two or more refrigerants whose equilibrium vapor and liquid phase compositions are the same at a given pressure. At this pressure, the slope of the temperature versus composition curve equals zero, which mathematically is expressed as ( dt / dx ) = 0, p which, in turn, implies the occurrence of a maximum, minimum, or saddle point temperature. Azeotropic blends exhibit some segregation of components at other conditions. The extent of the segregation depends on the particular azeotrope and the application. [ASHRAE 34:3]