ASHRAE Terminology

A Comprehensive Glossary of Terms for the Built Environment
ashrae.org/ashraeterms

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airflow rate (Q)

the volume of standard air per unit of time that moves past a given plane, expressed in cubic feet per minute (cfm) or liters per second (L/s).

cfm
exhaust terminal-unit total leakage

total amount of the air in cubic feet per minute (litres per second) drawn through the casing and a fully closed damper/valve into the airstream of an exhaust terminal unit at a given outlet pressure.

scfm

standard cubic feet per minute.

standard cubic feet per minute (SCFM)

the volumetric rate of flow of air that is at standard conditions.

terminal-unit casing leakage

air in cubic feet per minute (liters per second) leaking from a terminal unit at a given inlet pressure with the outlets and inlets blocked and with the damper/valve fully opened.

terminal-unit damper leakage

air in cubic feet per minute (liters per second) leaking through a fully closed damper/valve of a supply/exhaust terminal unit at a given inlet/discharge pressure.

ventilation rate

rate of airflow to or from a space, expressed in terms of volume per unit of time, either through the ventilation system or infiltration through building envelope. These are commonly expressed as cubic feet per minute (CFM) in USCS units or liters per second (l/s) in SI units.