What AFD size is required to achieve 4 air exchanges per hour in a room measuring 18 x 30 x 8 feet?

To determine the required airflow in cubic feet per minute (CFM) to achieve a specific number of air changes per hour in a room, several steps are involved.

First, calculate the volume of the room. The dimensions provided are 18 feet (width) x 30 feet (length) x 8 feet (height). Therefore, the volume of the room is:

Volume = Width x Length x Height = 18 ft x 30 ft x 8 ft = 4320 cubic feet.

Next, calculate the total air volume that needs to be changed in an hour to achieve 4 air changes. Since one air change involves replacing the entire volume of the room with fresh air, to achieve 4 air changes per hour, you multiply the room volume by 4:

Total Air Volume for 4 Changes = Volume x Air Changes = 4320 cubic feet x 4 = 17280 cubic feet per hour.

To convert this figure into CFM, which expresses the airflow in cubic feet per minute, divide the total air volume required per hour by the number of minutes in an hour (60 minutes):

CFM = Total Air Volume for 4 Changes / 60 minutes = 17280 cubic feet / 60 =