Industry
Testing industrial compressed air quality to ISO 8573
ISO 8573-1:2010 specifies compressed air purity classes for particles, water and oil, and the other parts of ISO 8573 give the test methods: oil aerosol in part 2, humidity in part 3, particles by number in part 4 and by mass in part 8, oil vapour in part 5 and liquid water in part 9.
Specifying the air
ISO 8573-1:2010 specifies purity classes of compressed air with respect to particles, water and oil, independent of where in the system the air is specified or measured. It also identifies gaseous and microbiological contaminants and links to the other parts of ISO 8573, either for measuring purity or for specifying purity requirements. On 22 October 2026, iso.org showed the 2010 edition as current (last confirmed in 2017) but at stage 90.92, to be revised, with a new edition, ISO/AWI 8573-1, under development.
Which part measures what
| Part | What it measures | Edition on iso.org (22 October 2026) |
|---|---|---|
| ISO 8573-2:2018 | Liquid oil and oil aerosols. Method A collects oil with inline coalescing filters; Method B uses sampling discs, solvent extraction and infrared spectrometry or gas chromatography. Oil vapour is excluded. | Edition 3, February 2018 |
| ISO 8573-3:1999 | Humidity (water vapour), with guidance on choosing a method. Water in states other than vapour is not covered. | Edition 1, June 1999; confirmed in 2017 |
| ISO 8573-4:2019 | Particle size and concentration by number, all particle types combined. | Edition 2, February 2019 |
| ISO 8573-5:2025 | Oil vapour, by pressurised sampling and gas chromatography. | Edition 2, July 2025 |
| ISO 8573-6:2003 | Gaseous contaminants: carbon monoxide, carbon dioxide, sulphur dioxide, nitric oxide, nitrogen dioxide and hydrocarbons C1 to C5. | Edition 1, May 2003; confirmed in 2025 |
| ISO 8573-7:2003 | Viable, colony-forming microbiological organisms, as distinct from other solid particles. | Edition 1, May 2003; to be revised |
| ISO 8573-8:2004 | Solid particles by mass concentration. | Edition 1, February 2004; confirmed in 2017 |
| ISO 8573-9:2004 | Liquid water content, as liquid water mass concentration. | Edition 1, February 2004; confirmed in 2017 |
Parts 4, 7, 8 and 9 each state that their methods are suitable for determining the purity classes of ISO 8573-1, and part 5 reports oil vapour in respect of the ISO 8573-1 purity class for oil. Part 4 counts all particles together without separating solid and liquid fractions, and part 9 leaves water vapour to part 3.
A class in a specification
In Portugal, the ACSS ET 08/2010 specification (V.2025) sets ISO 8573-1:2010 class [2:4:2] as the minimum quality for technical compressed air produced centrally or for hospitals.
Ultra Controlo
The ULTRAK activated carbon tower datasheet states an ISO 8573-1 quality class for oils of 0/1 and shows a dash for the solids and water classes; it gives a nominal residual oil vapour content below 0.003 mg/m³.
More questions
Which part of ISO 8573 measures oil vapour?
ISO 8573-5, whose 2025 edition uses pressurised sampling and gas chromatography. ISO 8573-2 covers liquid oil and oil aerosols and excludes oil vapour.
Is ISO 8573-1 being revised?
On 22 October 2026, iso.org showed ISO 8573-1:2010 as current but at stage 90.92, to be revised, with ISO/AWI 8573-1 under development.
Sources
- ISO 8573-1:2010 Compressed air, Part 1: Contaminants and purity classes (iso.org)
- ISO 8573-2:2018 Oil aerosol content (iso.org)
- ISO 8573-3:1999 Measurement of humidity (iso.org)
- ISO 8573-4:2019 Particle content (iso.org)
- ISO 8573-5:2025 Oil vapour content (iso.org)
- ISO 8573-6:2003 Gaseous contaminant content (iso.org)
- ISO 8573-7:2003 Viable microbiological contaminant content (iso.org)
- ISO 8573-8:2004 Solid particle content by mass concentration (iso.org)
- ISO 8573-9:2004 Liquid water content (iso.org)
- ACSS, Especificação Técnica ET 08/2010 V.2025, ar comprimido técnico
- ULTRAK datasheet, p. 2
Ultra Controlo figures come from its technical datasheets. Third-party facts were read at the source on the date shown.