ASHRAE Terminology

a diffuser, grille, register, or transfer grille used for controlling air patterns or air distribution or for preventing line of sight through an opening while allowing airflow through. See air terminal device or diffuser.

device or opening through which air is withdrawn from or discharged into a conditioned space (grilles, registers, diffusers, and slots may be used as air inlets).

any device (e.g., grille, register, diffuser) placed in an opening to a room, through which controlled air enters or leaves. Component of the air-distribution system which has the purpose of achieving the predetermined movement of air into or from a treated space.

series of air-directing vanes (usually adjustable) that are used to direct and/or control the combustion airflow through the burner.

total plane area of the portion of a grille, face, or register bounded by a line tangent to the outer edges of the outer openings, through which air can pass.

(1) actual open area between the fins of a grille or register. (2) total area through which air can pass in a grille, face, or register.

describes a building or space that has been specifically designated as historically significant by the adopting authority or is listed in The National Register of Historic Places or has been determined to be eligible for such listing by the U.S. Secretary of the Interior.

small bore tube inserted perpendicular to a flowing stream with its orifice facing the stream to measure total pressure. At present, the term is often used for a double-tube instrument from which the flow velocity can be calculated with one orifice facing the flowing stream to register total pressure and the other perpendicular to the stream to register static pressure.

combination grille and damper assembly over an air opening. See air outlet.

appropriately qualified and licensed professional engineer. See also design professional.

a device by which energy from a system is finally delivered, e.g., registers, diffusers, lighting fixtures, faucets, etc.