The scf and the scm are units of
molecular quantity for gases can be used with the
ideal gas law to compute the quantity per unit of volume for other pressures and temperatures. In spite of the label "standard", there is a variety of definitions, mainly depending on the type of gas. Since, for a given volume, the quantity is proportional to the
pressure and
temperature, each definition fixes base values for pressure and temperature.
Natural gas Since
natural gas is an imprecise mix of various molecular species, chiefly
methane but with varying proportions of other gases, a standard cubic foot of natural gas does not represent a precise unit of mass, but a molecular quantity, expressed in
moles. For petroleum gases, the standard cubic foot (scf) is defined as one
cubic foot of gas at and at normal sea level air pressure. The pressure definition differs between sources, but are all close to normal sea level air pressure. • A pressure of . This is the same pressure as the SI system standard pressure. Gives 1.1953
moles per scf. • A pressure of . The "M" refers to the Roman numeral for thousand, while a double "M" ("MM") represent one thousand thousands, or one million.
Bcf (billion standard cubic feet),
Tcf (trillion standard cubic feet),
Qcf (quadrillion standard cubic feet), etc., are also used.
Compressed or liquefied gases in refillable cylinders The
National Conference on Weights and Measures, a US-based non-profit organization working in cooperation with the US National Institute of Standards and Technology, has defined a set of standards in a regulation entitled the "Uniform Regulation for the Method of Sale of Commodities". This regulation defines a standard cubic foot, for compressed or liquefied gases in refillable cylinders
other than LPG by, "A standard cubic foot of gas is defined as a cubic foot at a temperature of 21 °C (70 °F) and a pressure of 101.325 kilopascals [kPa] (14.696 psia)". where, in the US, a standard cubic foot for industrial gas use is defined at and 14.696
psia (101.325 kPa), while in Canada, a standard cubic meter for industrial gas use is defined at and 101.325 kPa (14.696 psia). == Converting actual volumes to standard volumes ==