Gas Analyzer
Gas analysis techniques
Terms for gas analysis techniques Concentration
The term concentration describes the amount of a substance, expressed as mass, volume, or number of particles in a unit volume of a solid, liquid, or gaseous substance e.g. alcohol in beer or oxygen in air.
Different units are in use to describe concentration in gases:
Mass concentration
Concentration expressed in terms of mass of substance per unit volume [g substance/m3 gas volume]
¢ Volume concentration
Concentration expressed in terms of gaseous volume of substance per unit volume [cm3 substance/m3 gas volume]
Part concentration
Concentration expressed as number of particles of substance per a certain number of particles
In flue gas analysis both the terms mass concentration and part concentration are common and used in parallel. The mass unit is gram (and mg, g, see table 15) and the most popular expression for part concentration is ppm (parts per million). "ppm" means "x number of parts in a million parts". ppm is usually used for low concentrations; larger concentrations are expressed in "percent" (%), see table 16.
Consequently the concentration of a gaseous pollutant is expressed either using (or mg or g etc.) with reference to a definite gas volume, usually cubic metres (m3), e.g. 200 mg/m3 or using ppm without any reference, e.g. 140 ppm
Please note
Because of the variation of a gas volume with temperature and pressure changes it is necessary to use one of the following alternatives for describing a concentration value: additional specification of gas temperature and pressure values existing during measurement or conversion of the measured concentration value into the corresponding value at standard zero conditions, see the following chapter. After conversion, the volume is expressed as standard volume (standard cubic meter, Nm3 or m3N).
Standard zero conditions of a gas
The volume of a gas depends on its actual temperature and pressure. To achieve
Terms for gas analysis techniques Concentration
The term concentration describes the amount of a substance, expressed as mass, volume, or number of particles in a unit volume of a solid, liquid, or gaseous substance e.g. alcohol in beer or oxygen in air.
Different units are in use to describe concentration in gases:
Mass concentration
Concentration expressed in terms of mass of substance per unit volume [g substance/m3 gas volume]
¢ Volume concentration
Concentration expressed in terms of gaseous volume of substance per unit volume [cm3 substance/m3 gas volume]
Part concentration
Concentration expressed as number of particles of substance per a certain number of particles
In flue gas analysis both the terms mass concentration and part concentration are common and used in parallel. The mass unit is gram (and mg, g, see table 15) and the most popular expression for part concentration is ppm (parts per million). "ppm" means "x number of parts in a million parts". ppm is usually used for low concentrations; larger concentrations are expressed in "percent" (%), see table 16.
Consequently the concentration of a gaseous pollutant is expressed either using (or mg or g etc.) with reference to a definite gas volume, usually cubic metres (m3), e.g. 200 mg/m3 or using ppm without any reference, e.g. 140 ppm
Please note
Because of the variation of a gas volume with temperature and pressure changes it is necessary to use one of the following alternatives for describing a concentration value: additional specification of gas temperature and pressure values existing during measurement or conversion of the measured concentration value into the corresponding value at standard zero conditions, see the following chapter. After conversion, the volume is expressed as standard volume (standard cubic meter, Nm3 or m3N).
Standard zero conditions of a gas
The volume of a gas depends on its actual temperature and pressure. To achieve