Carbon dioxide equivalent of "emissions" or rate of greenhouse gas emission—a "flow" into the atmosphere—rather than the instantaneous value of the radiative forcing of the "stock" (concentration) of greenhouse gases "in the atmosphere" described by e. The carbon dioxide equivalency for a gas is obtained by multiplying the mass and the GWP of the gas. The following units are commonly used: For example, the GWP for methane over 100 years is 34 and for nitrous oxide 298. This means that emissions of 1 million metric tonnes of methane and nitrous oxide respectively is equivalent to emissions of 34 and 298 million metric tonnes
Industrial gas ambient temperature is low enough; this includes ethylene (R1150), carbon dioxide (R744), ethane (R170), nitrous oxide (R744A), and sulfur hexafluoride; however, these can only be liquefied under pressure if kept below their critical temperatures which are 9 °C for CH ; 31 °C for CO ; 32 °C for CH ; 36 °C for NO ; 45 °C for SF. All of these substances are also provided as a "Gas" (not a vapor) at the 200 bar pressure in a gas cylinder because that pressure is above their critical pressure. Other gases can only be supplied as liquid if also