The unit used to express the ventilation rate in the provided examples is which of the following?

The unit used to express the ventilation rate in the provided examples is which of the following?

• A. L/s
• B. CFM
• C. m3/h
• D. ACH

Answer: (B)

Ventilation rate is a volume of air moved per unit time. In many US HVAC contexts, the flow rate through a system is expressed in cubic feet per minute, or CFM. This unit directly measures how much air is passing by each minute, which matches how fans, ducts, and ventilation outputs are specified. The other units are metric equivalents (liters per second or cubic meters per hour) and are used in different regions, but the examples shown use the imperial unit CFM. Air changes per hour (ACH) describes how many times the room’s air would be replaced each hour, which is a rate based on room volume rather than the direct flow rate, and thus isn’t the unit for the ventilation rate itself.

Ventilation rate is a volume of air moved per unit time. In many US HVAC contexts, the flow rate through a system is expressed in cubic feet per minute, or CFM. This unit directly measures how much air is passing by each minute, which matches how fans, ducts, and ventilation outputs are specified. The other units are metric equivalents (liters per second or cubic meters per hour) and are used in different regions, but the examples shown use the imperial unit CFM. Air changes per hour (ACH) describes how many times the room’s air would be replaced each hour, which is a rate based on room volume rather than the direct flow rate, and thus isn’t the unit for the ventilation rate itself.