Ask the Expert Question-and-Answer Archive

by Ron Joseph

January, 2009

Exhaust Fan Motor Size

Q. If I have a 10'x10' open face spray booth and need 100 fpm air movement at the face, what size (CFM) motor do I need? Is there a formula for this?

A. You will need a fan that can deliver at least 10 ft x 10 ft x 100 ft/min = 10,000 CFM. To select the fan you must calculate or estimate the pressure looses in the exhaust system against which the fan will need to be able to draw. Any fan manufacturer should be able to assist you in selecting the correct fan, but insure that you tell the manufacturer that it is intended for use in a spray booth where volatile flammable fumes are emitted. You must insure that the fan and motor meet all applicable fire and safety codes.

Regards,

Ron Joseph