What is CFM?
CFM stands for Cubic Feet per Minute.

If an exhaust vent is rated at 50 CFM, that means that vent will intake 50 cubic feet of air per minute.


For Example: a 50 CFM Rated vent will intake all air in a 50 square foot room (5 ft wide x 10 ft long x 8 ft standard ceiling height) in 8 minutes.

5 X 10 X 8 = 400 cubic feet
400 cubic feet / 50 CFM = 8 minutes


The same vent will intake all air in a 100 square foot room (10 ft wide x 10 ft long x 8 ft standard ceiling height) in 16 minutes.

10 X 10 X 8 = 800 cubic feet
800 cubic feet / 50 CFM = 16 minutes