| ACH (Air Changes per Hour): |
The measurement of the complete replacement of inside air within a building area measured over an exact period of time. Education Note:An office or space which has its total air volume replaced in the time period of one hour experiences one Air Change per Hour. |
| Air Changes: |
A measurement method expressing the amount air movement into or out of a room or building by the number of building volumes of air, or room volumes of air, exchanged per hour. Air changes are described as AC/h or ACH |
| Air Exchange Rate: |
The rate (speed) at which the indoor air volume is to be exchanged one time from a building. Often, the air exchange rate is expressed in air changes per hour (ACH). |