# Normal cubic metre (Nm³)

A normal cubic metre (Nm³) is a cubic metre of gas stated at fixed reference conditions of temperature and pressure, not at the actual conditions; Commission Implementing Regulation (EU) 2018/2066 on greenhouse gas monitoring, for example, defines the standard conditions behind Nm³ as 273.15 K and 101,325 Pa.

WHO's Foundations of medical oxygen systems (2023) explains that an oxygen plant capacity in Nm³/h refers to a reference condition of temperature and pressure, that some capacities are given in Sm³/h, based on standard reference conditions, and that the units used determine the actual gas volume produced.

The [ULTRACON](https://library.ultracontrolo.com/products/ultracon/) concentrator table gives each model's oxygen output at 93% and at 95% in Nm³/h, Nl/min and SCFH, with its compressed air consumption in Nm³/h; at 93% it runs from 0.32 Nm³/h for model 1 to 111.4 Nm³/h for model 14D. The ULTRASCREW compressor datasheet uses another reference: it measures air flow in accordance with ISO 1217:2009, Annex C, with values referring to 1 bar absolute, 0% relative humidity and 20 °C inlet air.

## Sources

- [Commission Implementing Regulation (EU) 2018/2066, Article 3(52), consolidated text of 1 January 2025](http://publications.europa.eu/resource/celex/02018R2066-20250101)
- [WHO, Foundations of medical oxygen systems (17 February 2023), section 2.1](https://iris.who.int/server/api/core/bitstreams/4ad6f5fd-089e-4142-8439-b64e98d816d8/content)
- [ULTRACON datasheet, p. 3](https://www.ultracontrolo.com/products/ultracon)
- [ULTRASCREW datasheet, p. 3](https://www.ultracontrolo.com/products/ultrascrew)

Reviewed: 2026-10-22. Ultra Controlo engineering. https://library.ultracontrolo.com/glossary/normal-cubic-metre/