Air change


Also found in: Acronyms.

air change

[′er ‚chānj]
(engineering)
A measure of the movement of a given volume of air in or out of a building or room in a specified time period; usually expressed in cubic feet per minute.

Air change

The replacement of air contained within a room with an equivalent volume of fresh air.
References in periodicals archive ?
Monitored labs can run overall air change rates as low as 2 ACH when the air is clean, but can increase the airflow rates to 8 to 16 ACH when contaminants are sensed.
An additional standard of interest to designers of laboratories is ASHRAE Standard 129-1997, Measuring Air Change Effectiveness, which provides a method for determining the age of air in a space (or how well the outdoor air in the space is mixed within the space).
After determining the total air volume flow into (or flow out of) the building cluster, the air change rate of the building cluster can then be defined as,
This analysis indicates that minienvironment cleanrooms may be operated at lower air change rates without significantly affecting the cleanliness of the minienvironment, provided that the resulting higher particle concentrations in the cleanroom are of less concern.
When considering the operational air change rate, it is important that the design air change rate is correct for the activities and occupancy within the room.
In general, the discharge takes place through the chimneys and the compensation through the building body, which means that the air change rate in the studied buildings depends on their air tightness.
This ventilation strategy uses sensors to monitor spaces for a range of pollutants, allowing minimum air change rates during unoccupied periods to be reduced when pollutant levels are below some threshold value, saving thermal and fan energy related to once-through air.
Through comparing this result with the result of the ventilation measurement using the PFT technique, which determines the average air change rate during the entire period, the air change rate during periods of use--i.
The performance and energy efficiency of mini-environment cleanrooms depend on several factors including the design of mini-environment chamber, particle generation rate, associated air change rates for the mini-environment chamber as well as for the surrounding cleanroom space, and location and number of airflow supply and air return in the space.