# International Pharmacopoeia: medicinal oxygen monographs

The International Pharmacopoeia, published by WHO, defines medicinal oxygen in its 13th edition (2025) as one of three qualities: Oxygen 93% made by PSA or VSA, Oxygen 98% from two-stage adsorption plants, and Oxygen 99.5% made by cryogenic distillation.

## What the monograph covers

The International Pharmacopoeia (Ph. Int.) is the pharmacopoeia published by the World Health Organization. Its monograph Medicinal oxygen (Oxygenium medicinalis) was revised for the 13th edition, published in 2025, and now states that medicinal oxygen is Oxygen 93%, Oxygen 98% or Oxygen 99.5%. The text can be read online without a subscription, which makes it a practical public source for the impurity limits of oxygen 93.

| Quality | How it is produced | Oxygen content |
|---|---|---|
| Oxygen 93% | From ambient air by pressure swing adsorption (PSA) or vacuum swing adsorption (VSA) | 90.0% to 96.0% (V/V), the rest mainly argon and nitrogen |
| Oxygen 98% | Two-stage adsorption plant | Not less than 96.0% |
| Oxygen 99.5% | From ambient air by cryogenic distillation | At least 99.5% |

## Limits for Oxygen 93%

- Carbon dioxide: maximum 300 ppm (V/V).
- Carbon monoxide: maximum 5 ppm (V/V).
- Nitrogen monoxide and nitrogen dioxide: maximum 2 ppm (V/V) in total.
- Sulfur dioxide: maximum 1 ppm (V/V).
- Oil: maximum 0.1 mg/m3. Water: maximum 67 ppm (V/V).
- The oxygen content is monitored continuously during production.

## Edition in force and status

The 13th edition (2025) is the edition in force, and Medicinal oxygen appears on its list of revised texts. Older documents may cite earlier editions: the Global Fund briefing note on PSA plant oxygen purity, dated 3 April 2024, cites the 11th edition (2022). When a tender or specification refers to the International Pharmacopoeia, check which edition it names.

## What it means for a hospital or designer

- Mixtures: the monograph allows mixtures of the three qualities to be used clinically, but its requirements do not apply to any mixture. If one pipeline can receive both oxygen 93 and 99.5% oxygen, [ISO 7396-1](https://library.ultracontrolo.com/standards/iso-7396-1/) states that the concentration can vary between 90% and more than 99%.
- Bedside and home units: the monograph does not apply to oxygen produced by portable concentrators for home care or bedside use.
- National rules decide where each quality may be used. The Portuguese ACSS specification ET 03/2006 (revised June 2024), for example, restates the European Pharmacopoeia oxygen 93 limits and recommends a separate or dedicated distribution network for oxygen 93.

## Related standards

- Ph. Eur. 2455, Oxygen (93 per cent): the European monograph for oxygen from single-stage adsorption plants.
- [Ph. Eur. 3098](https://library.ultracontrolo.com/standards/ph-eur-3098-oxygen-98/), Oxygen (98 per cent): the European monograph for oxygen from two-stage adsorption plants.
- [Ph. Eur. 0417](https://library.ultracontrolo.com/standards/ph-eur-0417-oxygen/), Oxygen: the European monograph for cryogenic oxygen, minimum 99.5%.
- [USP Oxygen 93 Percent](https://library.ultracontrolo.com/standards/usp-oxygen-93/): the US monograph, 90.0% to 96.0% oxygen by volume.

ULTRAOX SC and ST PSA plants from Ultra Controlo state a purity of 94% (±1%) in their datasheets, which lies inside the 90.0% to 96.0% range of Oxygen 93%.

### Is the International Pharmacopoeia free to read?

Yes. The 13th edition (2025), including the Medicinal oxygen monograph, can be read online without a subscription.

### Does the monograph cover a mix of oxygen 93 and 99.5% oxygen?

No. Mixtures of the qualities may be used clinically, but the monograph requirements do not apply to any mixture.

### How much oxygen must Oxygen 98% contain?

Not less than 96.0% oxygen, produced by a two-stage adsorption plant.

## Sources

- [WHO, The International Pharmacopoeia, 13th edition (2025): Medicinal oxygen](https://digicollections.net/phint/202502/index.html#d/b.6.1.226)
- [WHO, The International Pharmacopoeia, 13th edition (2025): introduction and list of revised texts](https://digicollections.net/phint/202502/index.html#d/b.1)
- [ISO 7396-1:2016, Medical gas pipeline systems, Part 1 (iso.org)](https://www.iso.org/standard/60061.html)
- [ACSS ET 03/2006 v.2024, Especificações Técnicas para Gases Medicinais e Aspiração em Edifícios Hospitalares](https://www.acss.min-saude.pt/wp-content/uploads/2016/10/ET-03_2006_v2024-Gases-medicinais_VF.pdf)
- [Global Fund / BHI, 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)
- [ULTRAOX SC and ULTRAOX ST datasheets, p. 2](https://www.ultracontrolo.com/products/ultraox)

Reviewed: 2026-10-22. Ultra Controlo engineering. https://library.ultracontrolo.com/standards/international-pharmacopoeia-oxygen/