Annex 6 Usage of Units in Air Emissions
When reporting air concentrations, care must be taken with respect to the base units given. The following definitions apply:
m³ Cubic meter: is the SI unit of volume and may be used to express the volume of any substance, whether solid, liquid, or gas Nm³
Normal cubic meter: refers to the volume of any gas at 0°C and 1 atm (101.325 kPa)
In European countries and for emissions from municipal waste incinerators (also co-combustion of waste): Nm³ is defined at the following conditions: 101.325 kPa (= 1 atm), 273.15 K, dry gas, and 11% oxygen. For emissions from other types of combustion/thermal plants, there is no requirement to normalize to 11% oxygen.
Rm³ in Canada:
Reference cubic meter. When using R, the conditions are 25°C, 1 atm, dry. The need for oxygen correction should be explicitly stated, although it sometimes is not. The Canada-wide standard utilizes are correction to 11% oxygen for incinerators and coastal pulp and paper mill boilers burning salt-laden wood residue. For others sectors such as sinter plants, they have decided to use no oxygen correction.
Sm³ in U.S.A.:
Is the dry standard cubic meter (represented as dscm) at 1 atmosphere of pressure and 20 degrees Celsius (68 degrees F). The contaminant concentration is corrected to some standard percent oxygen or carbon dioxide in the combustion gases, usually 7% oxygen and 12% carbon dioxide.