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ACPH stands for Air changes per hour. It is air change rate, a measure of the air volume added to or removed from a space (normally a room or house) divided by the volume of the space.

Air changes per hour are the number of total replacements of any room's air in one hour. If the supply of the air by HVAC system in one hour is equal to the volume of the room then it will be one air change per hour.

ACPH is very important for indoor air quality.

For the typical home EPA recommends a rate of 0.35 ACH for healthy indoor air quality. The average home has a much higher rate of natural air infiltration than this.


How to Calculate Air Changes Per Hour

  1. Measure the length, width and height of your room in feet. ...
  2. Check your owner's manual to determine the capacity of the fan in cubic feet per minute.
  3. Multiply the capacity of your fan in cubic feet per minute by 60 to convert it to cubic feet per hour.