ISO 8573-2:2018 specifies test methods for the sampling and quantitative analysis of liquid oil and oil aerosols that can typically be present in compressed air. Test methods for oil vapour are excluded from this document as they are covered by ISO 8573‑5.

Two different methods are described, Method A and Method B. Method B is subdivided into two parts to clearly distinguish between procedures for obtaining the quantity of oil for analysis.

Method A describes an oil collection technique using inline coalescing filters whereas Method B utilizes sampling discs in a holder from which the collected oil is extracted with a solvent and analysed by infrared spectrometry or gas chromatography with flame ionization detection.

ISO 8573-2:2018 also includes descriptions of alternative oil aerosol detection by the use of indicator type devices, see Annex E.