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Cubic feet per minute (CFM) is an often confusing term because it has no single definition that applies to all instances. Gases are compressible , which means that a figure in cubic feet per minute cannot necessarily be compared with another figure when it comes the mass of the gas.
Actual cubic feet per minute (ACFM) is a unit of volumetric flow. It is commonly used by manufacturers of blowers and compressors. [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.
The SI unit is cubic metres per second (m 3 /s). Another unit used is standard cubic centimetres per minute (SCCM). In US customary units and imperial units, volumetric flow rate is often expressed as cubic feet per second (ft 3 /s) or gallons per minute (either US or imperial definitions).
With C v = 1.0 and 200 psia inlet pressure, the flow is 100 standard cubic feet per minute (scfm). The flow is proportional to the absolute inlet pressure, so the flow in scfm would equal the C v flow coefficient if the inlet pressure were reduced to 2 psia and the outlet were connected to a vacuum with less than 1 psi absolute pressure (1.0 ...
References will be made to "actual" flow rate through a meter and "standard" or "base" flow rate through a meter with units such as acm/h (actual cubic meters per hour), sm 3 /sec (standard cubic meters per second), kscm/h (thousand standard cubic meters per hour), LFM (linear feet per minute), or MMSCFD (million standard cubic feet per day).
A standard cubic foot (scf) is a unit representing the amount of gas (such as natural gas) contained in a volume of one cubic foot at reference temperature and pressure conditions. It is the unit commonly used when following the customary system , a collection of standards set by the National Institute of Standards and Technology .
If a filtering unit uses a MERV 12 filter that removes roughly 40% of the smoke particles, then it may still obtain a smoke CADR of 80 by filtering 200 cubic feet per minute instead of 100 CFM. Conversely, a 99.97% HEPA filter (MERV 17) that removes over 99.9% of the smoke particles needs to filter 80 cubic feet per minute to get a CADR of 80.
Q = Volumetric flow rate of air in cubic feet per minute (cfm) Vol = Space volume L × W × H, in cubic feet; In metric units = where: ACPH = number of air changes per hour; higher values correspond to more ventilation; Q = Volumetric flow rate of air in liters per second (L/s)