What is nominal cfm?

CFM (Displacement / Theoretical) measurements refer solely to the nominal capability of an air compressor’s pump – in other words, the actual volume of air the pump can displace (draw into the compressor) per minute. This figure is based upon the size of the pump’s cylinders and the speed at which the pump operates. A unit of flow is called the ACFM. Is this true? This is the actual gas delivery with reference to inlet conditions, which is an unqualified term, and should only be used in general and never accepted as a specific definition.