# ISO 8573-1 purity class

An ISO 8573-1 purity class is a rating of compressed air quality for particles, water and oil, written as three class numbers such as [2:4:2]; it is an industrial compressed air standard, while the quality of medical air is set by the pharmacopoeia.

ISO 8573-1:2010 specifies purity classes for compressed air with respect to particles, water and oil, and a quality is quoted as ISO 8573-1:2010 followed by the three classes in that order. [Class 0](https://library.ultracontrolo.com/glossary/class-0/) is the most stringent oil class. ISO lists the 2010 edition as current and due for revision.

ISO 8573-1 is an industrial compressed air standard, not a medical gas monograph. In Portugal, ACSS ET 08/2010 sets ISO 8573-1:2010 class [2:4:2] as the minimum quality for centrally produced technical compressed air, and the WHO interim technical specifications for PSA oxygen plants (2020, superseded by WHO's technical specifications of 31 December 2024) listed ISO 8573-1 among their product standards. Medical air is a medicine: the European Pharmacopoeia sets its limits in monograph 1238, Air, medicinal.

The ACIH hospital industrial air system from Ultra Controlo complies with ACSS ET 08/2010, and Ultra Controlo describes its oil-less ULTRACECO compressors as Class 0.

## Sources

- [ISO 8573-1:2010, Compressed air, Part 1: Contaminants and purity classes (ISO summary)](https://www.iso.org/standard/46418.html)
- [ACSS ET 08/2010 V.2025, Ar comprimido técnico (Portugal)](https://www.acss.min-saude.pt/wp-content/uploads/2016/10/ET-08_2010_V.2025_VF.pdf)
- [WHO, Technical specifications for PSA oxygen plants, interim guidance (2020)](https://www.who.int/publications/i/item/WHO-2019-nCoV-PSA_Specifications-2020.1)
- [EDQM Knowledge database, Ph. Eur. monograph 1238 Air, medicinal](https://extranet.edqm.eu/4DLink1/4DCGI/Web_View/mono/1238)
- [ACIH datasheet, p. 2](https://www.ultracontrolo.com/products/acih)
- [Ultra Controlo, Medical gas answers: glossary, Class 0](https://www.ultracontrolo.com/medical-gas-answers#term-class-0)
- [WHO, Technical specifications for health facility based medical oxygen systems (31 December 2024), note on the oxygen generator plant specification (supersedes the 2020 interim PSA specifications)](https://iris.who.int/server/api/core/bitstreams/ff437601-add3-44c8-8149-b85f0cdb2b52/content)

Reviewed: 2026-10-22. Ultra Controlo engineering. https://library.ultracontrolo.com/glossary/iso-8573-1-class/