# ISO 7396-3: proportioning units for synthetic medical air

ISO 7396-3:2025 is the ISO standard for proportioning units that mix oxygen and nitrogen to produce synthetic medical air, or air for driving surgical tools, as a source of supply for a medical gas pipeline; it is a new Part 3 of ISO 7396, first published in July 2025.

## Scope

ISO 7396-3 applies to devices that produce air by blending oxygen and nitrogen in defined proportions, for use as sources of supply in medical gas supply systems. It covers proportioning units that make synthetic medical air and units that make air for driving surgical tools.

It does not decide how many sources a supply system needs. The rule that a supply system consists of at least three sources of supply is outside ISO 7396-3 and is dealt with in [ISO 7396-1](https://library.ultracontrolo.com/standards/iso-7396-1/), which also governs the pipeline that the proportioning unit feeds.

## Edition and status

ISO 7396-3:2025 is edition 1, published in July 2025 by ISO/TC 121/SC 6 (27 pages), and was the current edition on 22 October 2026. It joins Part 1 (pipelines for compressed medical gases and vacuum) and [Part 2](https://library.ultracontrolo.com/standards/iso-7396-2/) (anaesthetic gas scavenging disposal systems).

## What it means for hospitals and designers

- It gives a standard reference for a medical air source that blends oxygen and nitrogen, as an alternative to air produced by compressors.
- The product is synthetic medical air, which has its own European Pharmacopoeia monograph, 1684 (Air, synthetic medicinal), separate from monograph 1238 for medicinal air.
- A proportioning unit is one source among the sources of supply; the number of sources and how they combine still follow ISO 7396-1.

## Ultra Controlo products

The ULTRAAR SC medical air plant uses totally oil-free ULTRACECO SC scroll compressors and, according to its datasheet, is built to EN ISO 7396-1: it makes medical air by compression, not by blending oxygen and nitrogen.

### Is synthetic medical air covered by the same monograph as medical air?

No. The European Pharmacopoeia has monograph 1238 for medicinal air and monograph 1684 for synthetic medicinal air.

### Does ISO 7396-3 say how many sources a supply system needs?

No. The rule of at least three sources of supply is left to ISO 7396-1.

## Sources

- [ISO 7396-3:2025, iso.org](https://www.iso.org/standard/86136.html)
- [ISO 7396-1:2016, iso.org](https://www.iso.org/standard/60061.html)
- [EDQM, Ph. Eur. monograph 1684 Air, synthetic medicinal](https://extranet.edqm.eu/4DLink1/4DCGI/Web_View/mono/1684)
- [EDQM, Ph. Eur. monograph 1238 Air, medicinal](https://extranet.edqm.eu/4DLink1/4DCGI/Web_View/mono/1238)
- [ULTRAAR SC datasheet, p. 2 and p. 3](https://www.ultracontrolo.com/products/ultraar-sc)

Reviewed: 2026-10-22. Ultra Controlo engineering. https://library.ultracontrolo.com/standards/iso-7396-3/