# How is medical air quality tested at commissioning?

**How is medical air quality tested and accepted when a new plant is commissioned?**

Under HTM 02-01 (2026), a new medical air plant is tested at the supply source before it feeds the pipeline, then at the terminal units for oxygen content, particles, water vapour, CO, CO2, SO2, nitrogen oxides and odour, with oil tested at the plant, against pharmacopoeial acceptance criteria.

HTM 02-01 (2026), the NHS England guidance for medical gas pipelines, divides commissioning into four phases: pre-commission tests and checks, tests on the pipeline carcass, tests of the complete system with test gas, and finally the identity, quality and purity tests on the medical gases by the Quality Controller (MGPS) before handover to clinical staff. Medical air quality belongs to the last phase. Other countries have their own rules, so the national specification applies outside England.

## Test the source first

For new installations, quality control testing is carried out at the supply source, such as the medical air compressor plant, before it is brought online, so that contamination is not introduced into the pipeline. The oil test is done at a plant test point before any pipeline is supplied by that plant.

## Tests at the terminal units

- Identity: for new installations every terminal unit is tested, and an oxygen analyser confirms 20.9% ± 0.5% oxygen for medical air; HTM 02-01 specifies a paramagnetic analyser for the identity of oxygen.
- Particles: every terminal unit is tested through a 47 mm diameter, 0.45 μm filter, at 150 L/min for 30 seconds for medical air, and on a new system the filter should be completely clear of visible particles.
- Water vapour: no more than 67 vpm, measured with an electronic test device.
- Gases: carbon monoxide up to 5 ppm, carbon dioxide up to 500 ppm, sulphur dioxide up to 1 ppm, and NO and NO2 up to 2 ppm.
- Odour: checked during purging and particulate testing, because several contaminants are detectable by odour.

## Who tests and what is recorded

Quality control testing is the responsibility of a Quality Controller (MGPS), who should not act as Authorised Person (MGPS) or Competent Person (MGPS) on the same project. HTM 02-01 asks for electronic analysers calibrated on site with certificated calibration gases; detector tubes can still be used for oil, CO, CO2, SO2, nitrogen oxides and water vapour. Results are recorded as numbers for each terminal unit and test point where possible, and the system is taken into use only once the medical gases are verified as fit for patient use.

The ULTRAAR SC and ESW pressure reduction sets include test valves, and the ULTRAAR ME set has two test valves to collect air samples. ULTRAAR SCA plants are tested before they leave the factory.

### Who carries out medical air quality tests in the UK?

A Quality Controller (MGPS) registered within the UK, who is not the Authorised Person (MGPS) or Competent Person (MGPS) on the project.

### What if the pipeline is not used straight after testing?

HTM 02-01 asks for a programme of purging and retesting, agreed with the Authorised Person (MGPS), when patient use does not follow the approval of the results.

## Sources

- [NHS England, HTM 02-01 Medical gas pipeline systems (2026), Part A, 19.28 and chapter 20](https://www.england.nhs.uk/wp-content/uploads/2016/05/health-technical-memorandum-02-01-medical-gas-pipeline-systems-part-a-design-installation-validation-verification-aug-2026.pdf)
- [ULTRAAR SC datasheet, p. 2](https://www.ultracontrolo.com/products/ultraar-sc)
- [ULTRAAR ESW datasheet, p. 3](https://www.ultracontrolo.com/products/ultraar-esw)
- [ULTRAAR ME datasheet, p. 3](https://www.ultracontrolo.com/products/ultraar-me)
- [ULTRAAR SCA datasheet, p. 4](https://www.ultracontrolo.com/products/ultraar-sca)

Reviewed: 2026-10-22. Ultra Controlo engineering. https://library.ultracontrolo.com/answers/how-is-medical-air-tested-at-commissioning/