This part of ISO 8573 specifies the gas chromatography test method for determining the content of oil vapour (hydrocarbons of six or more carbon atoms) in compressed air, regardless of the source of the compressed air, as well as of any organic solvents in the vapour, difficult to separate from the other hydrocarbons. It also gives guidelines on the use of chemical indicator tubes as an initial indication of the presence of oil vapour. This part of ISO 8573 elaborates sampling, measurement, evaluation, uncertainty considerations and reporting in respect of the compressed air purity class parameter, oil vapour, in accordance with ISO 8573-1. NOTE Lighter hydrocarbons composed of five or less carbon atoms are dealt with as gaseous contaminants in 8573-6.