# Oxygen flowmeter

In the 2019 WHO-UNICEF technical specifications and guidance for oxygen therapy devices, an oxygen flowmeter is a device that measures and controls the rate of oxygen flow to a patient, from a pipeline terminal unit, a high-pressure cylinder or a concentrator.

ISO 15002:2023 covers flow control devices connected to an ISO 9170-1 terminal unit of an ISO 7396-1:2016 pipeline, or to the pressure outlet of a regulator, in three types: flowmeters, flowgauge devices and fixed orifice devices. It does not apply to devices for use with gases for driving surgical tools. WHO-UNICEF (2019) describes three types: the Thorpe tube, or rotameter, which has a float in an upright clear tube, must be used vertically and is calibrated to a specific gas; the Bourdon gauge; and the dial/click type. It prefers a compensated flowmeter because it shows when an obstructed or pinched line delivers too little oxygen.

HTM 02-01 (2026), the NHS England guidance, warns that oxygen and medical air flowmeters read differently if interchanged, and that a normal ward flowmeter (0 to 15 L/min) should not be used where a paediatric flowmeter (0 to 1.5 L/min) is required. Ultra Controlo supplies medical oxygen and air flowmeters in various flow ranges for ICU, ward and theatre use, which connect directly to NIST, DISS and "Schraeder" wall outlets.

## Sources

- [WHO-UNICEF, Technical specifications and guidance for oxygen therapy devices (14 January 2019)](https://iris.who.int/server/api/core/bitstreams/5a996b5a-6803-486e-bccb-98efc398118d/content)
- [ISO 15002:2023, Flow control devices for connection to a medical gas supply system (ISO summary)](https://www.iso.org/standard/75973.html)
- [HTM 02-01 (2026) Part B, paragraphs 9.173 and 9.174 (NHS England)](https://www.england.nhs.uk/wp-content/uploads/2016/05/health-technical-memorandum-02-01-medical-gas-pipeline-systems-part-b-operational-management-aug-26.pdf)
- [Ultra Controlo, medical oxygen and air flowmeter](https://www.ultracontrolo.com/accessories/flowmeter)

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