Enter the volumetric flow rate, the width, and the height of the area into the calculator to determine the air exchange per hour and per minute.

Air Exchange Formula

The following formula is used to calculate the rate of air exchange. 

AER = Q/V
  • Where AER is the air exchange rate in exchanges per time.
  • Q is the volumetric flow rate (typically cubic feet per minute or hour)
  • V is the volume of the room (ft^3)

To calculate an air exchange rate, divide the volumetric flow rate by the volume of the room.

Air Exchange Definition

Air exchange is defined as the rate of change of units of air moving through a given volume at any time. Typically this is in reference to the number of air changes per time for a room or indoor area. This helps determine the ventilation of the area.

Example Problem

How to calculate air exchange?

First, determine the volumetric flow rate of the air moving through the room. This is typically measured in cubic feet per minute or cubic feet per hour but it can be any volumetric flow rate unit.

In this example problem, the volumetric flow rate is found to be 500 cubic feet per hour.

Next, determine the volume of the room. For this example problem, the dimensions of the room are 5 feet, 10 feet, and 6 feet for width, length, and height respectively.

To calculate the volume, multiply the length, width, and height together. 5*10*6 = 300 ft^3.

Finally, calculate the number of air exchanges per hour and per minute.

Using the formula above we find the number of air exchanges per hour to be:

500/300 = 1.666 changes per hour.

Divide this result by 60 to get the number of exchanges per minute.

= 1.666 / 60 = .0277 exchange per minute.