A method of expressing the amount of air infiltration and/or ventilation of a building or room in terms of the number of building volumes or room volumes exchanged per unit of time.
The replacement of a quantity of air in a space within a given period of time, typically expressed as air changes per hour. If a building has one air change per hour, this is equivalent to all of the air in the building being replaced in a one–hour period.
A measure of the amount of air moving in or out of a space because of leakage or mechanical ventilation. One air change is a volumetric flow of air equal to the cubic content of the space.
A measure of the rate at which the air in an interior space is replace by outside (or conditioned) air by ventilation and infiltration; usually measured in cubic feet per time interval (hour), divided by the volume of air in the room.
The amount of air required to completely replace the air in a room or building; not to be confused with recirculated air.
A measure of the amount of air moving into and out of a space. One air change is a volumetric flow of air equal to the cubic content of the space. Example: If a space has a cubic content of 10,000 cubic feet and the ventilation rate is 1000 cfm, then 0.1 (1000/10,000) air change is occurring every minute, or 6 (60x0.1) air changes are occurring per hour.
volume of air recirculating through a cleanroom per minute divided by the volume of the room. Generally the lower the cleanroom class the higher the air changes. A class 1000, class 100, class 10 and class 1, Cleanroom should have 5-6, 7, 7-10, and 10 air changes per minute respectively.
