ISO 12141:2002 describes a reference method for the measurement of low dust content in ducted gaseous streams at concentrations below 50 mg/m3 under standard conditions. This method has been validated with special emphasis on the region around 5 mg/m3. ISO 12141:2002 has been developed and validated for gaseous streams emitted by waste incinerators. More generally, it may be applied to emissions from other stationary sources, and to higher concentrations. If the gases contain unstable, reactive or semi-volatile substances, the measurement will depend on the sampling and filter treatment conditions.