Ambient pressure concept of pressure becomes irrelevant, and it is undefined at a gravitational singularity. The SI unit of pressure is the pascal (Pa), which is a very small unit relative to atmospheric pressure on Earth, so kilopascals (kPa) are more commonly used in this context. The ambient atmospheric pressure at sea level is not constant: it varies with the weather, but averages around 100 kPa. In fields such as meteorology and underwater diving, it is common to see ambient pressure expressed in bar or millibar. One bar is 100 kPa or approximately ambient pressure at sea level. Ambient pressure may in
Standard cubic foot "M's" 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. 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