NFPA-90A-2002 Standard for the Installation of Air-Conditioning and Ventilating Systems.
3.2.4 Shall. lndicaes a mandatory requirement.
3.2.5 Should. Indicates a recommendation or that which is advised but TiOt required.
3.3 General Definitions.
3.3.1 Accessible. Capable of being removed or exposed withOut damaging the building structure or finish, or not permanently closed in by the structure or finish of the building.
3.3.2 Air Cleaner. A device used to reduce or remove airborne solids from heating, ventilating, and air-condi tioTli ng systems by electrostatic means,
333* Air Connector. A conduit for transferring air between an air duct or plenum and an air terminal unit or an air inlet or air outlet.
3.3.4 Air Distribution System. A continuous passageway for the transmission of air that, in addition to air ducts, can in- chide air connectors, air duct fittings, dampers, plen urns, fans, and accessory air-handling equipment but that does not incit ide conditioned spaces.
3.3.5 Air Duct. A conduit or passageway for conveying air to or from heating, cooling, air conditioning, or ventilating equipment, but not including the plenum. [97:1.2]
3.3.6 Air Duct Covering. A material such as an adhesive, insulation, banding, a coating(s), film, or ajacket used to cover the outside surface of an air duct, fan casing, or duct pleninn.
3.3.7 Air Duct Lining. A material such as an adhesive, insulation, a coating(s), or film used to line the inside surfce of an air duct, Fan casing, or duct pleTlurn.
3.3.8 Air Filter. A device used to reduce or remove airborne solids from heating, ventilating, and air conditioning.
33•9* Air Inlet. Any opening through which air is removed from a space and returned to an air distribution system.
3.3.10* Air Outlet. Any opening through which air is delivered to a space from an air distribution system.
3.3.11 Air Terminal Unit. An appliance receiving, conditioning, and delivering air supplied through an air distribution system.
3.3.12 Air Transfer Opening. An opening designed to allow the movement of environmental air between two contiguous spaces.
3.3.13 Damper.
3.3.13.1* Ceiling Radiation Damper. A device installed to limit radiant heat transfer through an air outlet or air inlet opening in the ceiling of a floor- or roof-ceiling assenibly having not less than a 1-hour fire resistance rating. Such a device is described in the construction details for some tested floor- or roof-ceiling assernl)lies,
3.3.13.2 Combination Fire and Smoke Damper. A device that meets both the fire damper and smoke damper requirements.
NFPA-90A pdf download.