How is the identity and purity of gas checked at each outlet before handover?

Under HTM 02-01, the NHS England guidance, outlets get two sets of checks before handover: engineering tests proving each outlet is gas-specific and no pipes are cross-connected, then quality control tests in which an independent Quality Controller analyses the gas at the outlets for identity and quality. On a new pipeline, every outlet is tested.

Who signs off the gas at the outlets?

In the UK, a registered Quality Controller (MGPS), independent of the engineers on the project, confirms identity and quality; the Designated Clinical Officer then takes the area back into use.

Are outlets retested after a repair?

Yes. HTM 02-01 asks for quality control testing after planned work that interrupts the supply and after any unplanned interruption.

Which instrument confirms oxygen identity?

HTM 02-01 specifies a paramagnetic oxygen analyser.

How is gas identity and purity checked at each outlet?

The sequence below follows HTM 02-01 (2026) Part A, the NHS England guidance, which treats medical gases as medicines. ISO 7396-1 also covers testing and commissioning, and the Portuguese ACSS specification asks for tests according to ISO 7396-1 and ISO 7396-2.

Step 1: engineering tests

Outlet tests: each outlet is checked for the correct service and compliance with BS EN ISO 9170-1, that it resists rotation and retains its probe, that it is labelled, and that static and flow pressures are right, using a test gun with a gas-specific probe.
Particulate test: every outlet on a new system is tested with a membrane filter at not less than 150 L/min for 30 s, and the filter should show no visible particles.
Cross-connection test: in two stages, from the plant to the area valves and from the area valves to the outlets, with each gas supplied in turn. For example, with oxygen and vacuum live and medical air isolated, oxygen outlets should show pressure, air outlets no pressure and vacuum outlets suction. The test is repeated after any later modification.

Step 2: quality control by an independent Quality Controller

Quality control is the final, independent check of gas identity and quality. It is done by a Quality Controller (MGPS), not by the Authorised or Competent Persons working on the project, after a new installation, after planned work that interrupts the supply, and after any unplanned interruption.

Coverage: on a new pipeline, or where shield gas was used in a modification, all outlets are tested; otherwise a risk-assessed sample that includes new outlets and those at the ends of lines. Testing starts at the outlets furthest from the area valve.
Identity: the gas should be positively identified, not inferred. A paramagnetic analyser is the specified instrument for oxygen; nitrous oxide is checked by thermal conductivity or infrared. Where oxygen and nitrous oxide outlets share a bank, the oxygen is tested for the absence of nitrous oxide.
Quality: particulates with a 47 mm, 0.45 µm filter at every outlet; water vapour not above 67 vpm, about -46 °C atmospheric dew point; carbon monoxide not above 5 ppm; and the other limits set in HTM 02-01.

Handover

"Do not use" plugs stay in the outlets, and no medical equipment is connected, until validation and verification are complete. The Designated Clinical Officer then takes the area back into use once the gases have been tested and verified. HTM 02-01 says its tests supplement the pharmacopoeial tests by focusing on the pipeline; for oxygen 93, the European Pharmacopoeia monograph itself defines the quality of the gas delivered to the pipeline, not at the outlet.