At an ambient sea level atmospheric pressure of 1 atm (101.325 kPa or 1.01325 bar), the general equation is: and for the reverse conversion: Notes: Air pollutant concentrations expressed as mass per unit volume of atmospheric air (e.g., mg/m3, μg/m3, etc.)
Some governmental regulatory jurisdictions require industrial sources of air pollution to comply with sea level standards corrected for altitude.
In other words, industrial air pollution sources located at altitudes well above sea level must comply with significantly more stringent air quality standards than sources located at sea level (since it is more difficult to comply with lower standards).
Environmental agencies in the USA often use the terms "dscf" or "scfd" to denote a "standard" cubic foot of dry gas.
Likewise, they often use the terms "dscm" or "scmd" to denote a "standard" cubic meter of gas.