# WHO technical specifications for PSA oxygen plants

The WHO Technical specifications for PSA oxygen plants (interim guidance, 8 June 2020) specified minimum requirements for PSA plants producing medical oxygen 93% ± 3 from ambient air; WHO's Technical specifications for health facility based medical oxygen systems (31 December 2024) state that their oxygen generator plant specification supersedes them.

## What the specification asked for

| Item | WHO interim specification (2020) |
|---|---|
| Product | Medical oxygen 93% ± 3 from ambient air, by pressure swing adsorption |
| Low-purity alarm | Alarm when the oxygen concentration is lower than 90% |
| Output pressure | Continuous 300 to 600 kPa (3 to 6 bar) |
| Typical output | From 2 Nm³/h to 200 Nm³/h |
| Feed air compressor | Oil-free, or filtered oil-injected or oil-lubricated rotary screw; minimum 750 kPa |
| Life span | At least 10 years, guaranteed by a letter from the manufacturer |
| Warranty and spares | 48 months, with option to extend; 3-year spare parts kit |
| Installation | Conformity verified by a certified third party |
| Manufacturer | Certified quality management system for medical devices, for example ISO 13485 or ISO 9001 |

## Status: interim guidance

WHO published the document, reference WHO/2019-nCoV/PSA_Specifications/2020.1, on 8 June 2020 during the COVID-19 response. The text stated that, as interim guidance, it would expire two years after publication, yet WHO still hosts it. WHO's [Technical specifications for health facility based medical oxygen systems](https://library.ultracontrolo.com/standards/who-technical-specifications-health-facility-oxygen-systems/), published on 31 December 2024, state that their oxygen generator plant specification supersedes this interim guidance. Cite it as WHO interim technical specifications (2020), not as a WHO approval of any plant or manufacturer. It also reflected the standards of its time: it referenced the 2018 edition of [NFPA 99](https://library.ultracontrolo.com/standards/nfpa-99/), whose current edition is 2027.

## What it means for hospitals and buyers

- Used as a tender checklist, each item should be checked against the current editions of the standards it cited and against national rules.
- The purity band of 93% ± 3 is the oxygen 93 range of 90% to 96% used in [ISO 7396-1](https://library.ultracontrolo.com/standards/iso-7396-1/) and in Ph. Eur. 2455; WHO's Foundations of medical oxygen systems (2023) repeats that generator plant purity should be 93% ± 3%.
- A Global Fund briefing note (3 April 2024) shows why the band matters for capacity: a PSA plant giving 20 Nm³/h at 93% ± 3% would give 18 Nm³/h if set to 95% ± 1%.

## Ultra Controlo products

Ultra Controlo is certified to ISO 13485:2016. Its ULTRAOX SC and ST datasheets state an oxygen purity of 94% (±1%) and an oxygen outlet pressure of 6 bar.

### Is the WHO PSA specification still valid?

It was issued as interim guidance on 8 June 2020, stated that it would expire two years after publication and, according to WHO's technical specifications of 31 December 2024, is superseded by the oxygen generator plant specification in that document. Use it as a reference checklist, not as a current standard.

## Sources

- [WHO, Technical specifications for PSA oxygen plants (publication page)](https://www.who.int/publications/i/item/WHO-2019-nCoV-PSA_Specifications-2020.1)
- [WHO, Technical specifications for PSA oxygen plants (PDF)](https://iris.who.int/server/api/core/bitstreams/d53996d5-380c-44ae-9fe8-9e529d3270cd/content)
- [WHO, Technical specifications for health facility based medical oxygen systems (31 December 2024), publication page](https://www.who.int/publications/i/item/9789240101616)
- [WHO, Technical specifications for health facility based medical oxygen systems (2024), PDF, section 1.1](https://iris.who.int/server/api/core/bitstreams/ff437601-add3-44c8-8149-b85f0cdb2b52/content)
- [WHO, Foundations of medical oxygen systems (2023)](https://iris.who.int/server/api/core/bitstreams/4ad6f5fd-089e-4142-8439-b64e98d816d8/content)
- [Global Fund, Briefing Note: PSA Plant Oxygen Purity (3 April 2024)](https://resources.theglobalfund.org/media/lenpqaoa/cr_c19rm-psa-oxygen-purity_technical-briefing-note_en.pdf)
- [ISO 7396-1:2016, iso.org](https://www.iso.org/standard/60061.html)
- [NFPA, NFPA 99 code development page](https://www.nfpa.org/codes-and-standards/nfpa-99-standard-development/99)
- [ULTRAOX SC datasheet, p. 2 and p. 5](https://www.ultracontrolo.com/products/ultraox)
- [ULTRAOX ST datasheet, p. 2 and p. 5](https://www.ultracontrolo.com/products/ultraox-st)
- [Ultra Controlo, Medical gas answers: certifications](https://www.ultracontrolo.com/medical-gas-answers#ultra-controlo-certifications)

Reviewed: 2026-10-22. Ultra Controlo engineering. https://library.ultracontrolo.com/standards/who-psa-plant-specifications/