This International Standard/Recommendation specifies the metrological and technical requirements and tests for measuring instruments [hereafter termed "instrument(s)"] that serve to determine the volume fractions of certain components of the exhaust gases emanating from motor vehicles, and establishes the conditions with which such instruments must comply in order to meet any OIML performance requirements.
It is applicable to instruments, particularly those used according to the procedure defined in ISO 3929, intended for the inspection and maintenance of in-use motor vehicles with spark ignition engines. These instruments are used to determine the volume fraction of one or more of the following exhaust gas components:
— carbon monoxide (CO);
— carbon dioxide (C02);
— hydrocarbons (HC, in terms of n-hexane); and
— oxygen (02)
at the moisture level of the sample as analysed.
This International Standard/Recommendation covers instruments whose principle of detection is based on infrared absorption in gases for CO, C02 and HC. Oxygen is generally measured with a fuel cell. It is not intended, however, to exclude any other types of instruments that, although based on other principles of detection, meet the specified metrological and technical requirements and satisfy the associated tests. Three accuracy classes of the instruments, Class 0, Class I and Class II, are covered.