ICFM

ICFM is inlet cubic feet per minute, the volumetric airflow measured at the compressor’s inlet flange under the inlet pressure, temperature, and humidity that the machine actually sees. It is sometimes called “actual inlet flow” and is closely related to ACFM, with the distinction that ICFM accounts for the pressure drop across the inlet filter and any inlet piping.

What it is

Where ACFM describes the volume of free air outside the compressor, ICFM describes the volume after inlet losses. Inlet filters, silencers, and elbows reduce the absolute pressure presented at the rotor or piston, so the gas occupies more volume than the ambient ACFM. Engineering teams use ICFM when modeling rotor displacement or when verifying that a new inlet filter will not starve a machine.

Why it matters

For most buyers, ICFM is a back-office number. It matters when troubleshooting capacity loss: a clogged inlet filter raises ICFM relative to ACFM, which sounds backward but reflects the lower inlet pressure. Field service techs use the relationship to diagnose intake restriction without disassembly.

How it is used in our catalog

Our catalog publishes SCFM at rated pressure. ICFM appears in the underlying CAGI data sheets we link from each compressor entry, useful for engineers doing inlet system design. Browse rotary screw compressors for CAGI sheets that report ICFM alongside the headline flow.

Common questions

Is ICFM the same as displacement?

No. Displacement is the theoretical geometric volume swept by the rotor or piston per minute. ICFM is the actual volumetric flow at the inlet flange, always somewhat less than displacement because of slip and re-expansion losses.

Will I see ICFM on a quote?

Rarely. Sales documents list SCFM. ICFM appears in engineering data sheets and is the right number for inlet system design.