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Standard sea-level conditions (SSL), [1] also known as sea-level standard (SLS), defines a set of atmospheric conditions for physical calculations. The term "standard sea level " is used to indicate that values of properties are to be taken to be the same as those standard at sea level, and is done to define values for use in general calculations.
For example, IUPAC has, since 1982, defined standard reference conditions as being 0 °C and 100 kPa (1 bar), in contrast to its old standard of 0 °C and 101.325 kPa (1 atm). [2] The new value is the mean atmospheric pressure at an altitude of about 112 metres, which is closer to the worldwide median altitude of human habitation (194 m).
A normal cubic meter (Nm 3) is the metric expression of gas volume at standard conditions and it is usually (but not always) defined as being measured at 0 °C and 1 atmosphere of pressure. A standard cubic foot (scf) is the USA expression of gas volume at standard conditions and it is often ( but not always ) defined as being measured at 60 ...
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).
For petroleum gases, the standard cubic foot (scf) is defined as one cubic foot of gas at 60 °F (288.7 K; 15.56 °C) and at normal sea level air pressure. The pressure definition differs between sources, but are all close to normal sea level air pressure.
Standard cubic feet per minute (SCFM) is the molar flow rate of a gas expressed as a volumetric flow at a "standardized" temperature and pressure thus representing a fixed number of moles of gas regardless of composition and actual flow conditions.
Ratings found in centrifugal fan performance tables and curves are based on standard cubic feet per minute (SCFM). Fan manufacturers define standard air as clean, dry air with a density of 0.075 pounds mass per cubic foot, with the atmospheric pressure at sea level of 29.92 inches of mercury and a temperature of 70°F.
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).