[1] This is the actual gas delivery with reference to inlet conditions, whereas cubic foot per minute (CFM) is an unqualified term and should only be used in general and never accepted as a specific definition without explanation.
Actual cubic feet per minute is the volume of gas and air flowing anywhere in a system independent of its density.
Ratings found in centrifugal fan performance tables and curves are based on standard cubic feet per minute (SCFM).
Selecting a centrifugal fan to operate at conditions other than standard air requires adjustment to both static pressure and brake horsepower.
If a centrifugal fan is to operate at a non-standard density, then corrections must be made to static pressure and brake horsepower.
Centrifugal fans that are specified for continuous operation at higher temperatures need to be selected taking into account air density corrections.
AMCA Standard 210 defines uniform methods for conducting laboratory tests on housed fans to determine airflow rate, pressure, electric power and energy efficiency, at a given speed of rotation.
The purpose of AMCA Standard 210 is to define exact procedures and conditions of fan testing so that ratings provided by various manufacturers are on the same basis and may be compared.