# WHO Foundations of medical oxygen systems (2023)

Foundations of medical oxygen systems is a 92-page World Health Organization reference document dated 17 February 2023 (WHO/2019-nCoV/Clinical/Oxygen/2023.1, corrigenda of 3 November 2023) that compiles definitions, technical requirements, tools and resources for medical oxygen systems, with five web annexes, mostly on procuring, siting and commissioning oxygen generator plants.

## What it covers

WHO compiled the document to capture definitions, technical requirements, tools and resources related to medical oxygen systems, for national authorities, policy-makers, donors, implementing partners, practitioners and biomedical engineers. It has five main sections:

- Oxygen history, ecosystem and related systems.
- Health facility oxygen systems: onsite production (PSA, VSA and VPSA), technical requirements and sizing of PSA plants, cylinder filling, changeover systems, high-pressure cylinders, medical gas pipeline systems and onsite liquid oxygen.
- Operationalization of oxygen systems, including estimation of oxygen demand.
- Offsite oxygen production.
- Tools and resources.

Its five web annexes are: A, technical considerations for the procurement of oxygen generator plants; B, site evaluation; C, site readiness; D, commissioning report; and E, oxygen supplier's mapping.

## Key technical statements

- The purity of concentrated oxygen from generator plants should be 93% ±3%.
- PSA plants use a compressor to push air through the sieve beds; VSA plants use a vacuum system to draw air in, and their lower output pressure generally adds the need for an oil-free booster compressor. WHO puts VSA capital cost about 15% above PSA because of that booster, a margin that drops off when units generate more than 100 Nm³/h.
- WHO names ISO 7396-1, HTM 02-01 and NFPA 99 as the three reference standards widely used for pipeline design.
- For high-pressure cylinders, it states that the entity responsible for refilling must oversee maintenance every 5 years, with at least a hydrostatic test, a weight loss test (> 5%) and a corrosion test, and it names the EU TPED, which requires a Pi mark on the cylinder shoulder.

## Status and type

WHO lists the document under COVID-19 clinical care, with reference WHO/2019-nCoV/Clinical/Oxygen/2023.1, dated 17 February 2023 and with corrigenda of 3 November 2023. It is a compilation; WHO's [technical specifications for health facility medical oxygen systems](https://library.ultracontrolo.com/standards/who-technical-specifications-health-facility-oxygen-systems/) (31 December 2024) give the product specifications and point back to the Foundations for an overview of system design. In UNDP procurement, [REQ-OXY-001](https://library.ultracontrolo.com/standards/undp-req-oxy-001/) (in force since 1 January 2025) lists web annex A among its references.

## Points to watch

- Its HTM 02-01 reference is the 2006 edition; NHS England published a new edition of HTM 02-01 on 19 August 2026.
- It cites the 10th edition (2020) of The International Pharmacopoeia; the current edition is the 13th, published in 2025 ([medicinal oxygen monograph](https://library.ultracontrolo.com/standards/international-pharmacopoeia-oxygen/)).
- It refers to WHO's 2020 [PSA plant specifications](https://library.ultracontrolo.com/standards/who-psa-plant-specifications/), which WHO's 2024 technical specifications state they supersede.

### What kind of document is Foundations of medical oxygen systems?

WHO describes it as compiled to capture definitions, technical requirements, tools and resources related to medical oxygen systems; product specifications are in WHO's 2024 technical specifications.

### Which pipeline standards does it name?

ISO 7396-1, HTM 02-01 and NFPA 99, as the three reference standards widely used for medical gas pipeline design.

### What purity does it give for PSA oxygen?

It states that the purity of concentrated oxygen from generator plants should be 93% ±3%.

## Sources

- [WHO, Foundations of medical oxygen systems (17 February 2023), publication page](https://www.who.int/publications/i/item/WHO-2019-nCoV-Clinical-Oxygen-2023.1)
- [WHO, Foundations of medical oxygen systems (17 February 2023), PDF](https://iris.who.int/server/api/core/bitstreams/4ad6f5fd-089e-4142-8439-b64e98d816d8/content)
- [WHO, Technical specifications for health facility based medical oxygen systems (31 December 2024), PDF](https://iris.who.int/server/api/core/bitstreams/ff437601-add3-44c8-8149-b85f0cdb2b52/content)
- [UNDP, REQ-OXY-001 V01, Technical & Regulatory Requirements for Oxygen Plants (effective 1 January 2025)](https://healthimplementation.undp.org/wp-content/uploads/2025/01/REQ-OXY-001-v01-UNDP-TECHNICAL-REGULATORY-REQUIREMENTS-FOR-OXYGEN-PLANTS.pdf)
- [NHS England, Health Technical Memorandum 02-01: Medical gas pipeline systems (publication page)](https://www.england.nhs.uk/publication/health-technical-memorandum-02-01-medical-gas-pipeline-systems/)
- [The International Pharmacopoeia, 13th edition (2025)](https://digicollections.net/phint/202502/index.html#d/b.1)

Reviewed: 2026-10-22. Ultra Controlo engineering. https://library.ultracontrolo.com/standards/who-foundations-of-medical-oxygen-systems/