How is an anaesthetic gas scavenging system tested and re-commissioned?

Under the NHS England guidance HTM 02-01 (2026), an anaesthetic gas scavenging system is tested by running the plant under full load for one hour, checking pump rotation and current, and measuring extract flow at every terminal unit with a test device and metered leaks, then fully recommissioned at least every 12 months.

Who witnesses AGSS tests?

Under HTM 02-01 (2026) the contractor usually carries out the tests and the Authorised Person (MGPS) witnesses them.

What flow is set at each terminal unit?

In HTM 02-01 recommissioning, the lowest flow for the system set-up, for example 50 L/min or 80 L/min, with the system at the lowest pressure that achieves it and the terminal units fully open.

How is an anaesthetic gas scavenging system tested?

HTM 02-01 (2026) notes that BS EN ISO 9170 specifies the tests to be carried out on AGSS. In general the contractor carries out the tests and the Authorised Person (MGPS) witnesses them; the results are recorded on form B12.

At commissioning

Run all equipment continuously under full load for one hour (19.163).
Check the direction of rotation and the current drawn by each powered device at full load (19.164).
Test the disposal system against the HTM performance criteria, with the number of terminal units it was designed for in use (19.165).
Insert a test device and metered leaks to replicate the design flow, repeat the measurements, and move the test device until every terminal unit has been tested. The test device replicates the type of receiving system the plant was designed for (19.166 and 19.167).
Apply diversity: in a typical theatre suite only one receiving system per operating room is in use, so two metered leaks are used, one in an operating room terminal unit and one in the anaesthetic room terminal unit (19.168).
Check user switches, power-on indicators and alarms, any PIR or ventilation set-back control including the run-on timer, and the mechanical operation and check valve of each terminal unit (19.169 to 19.171).

Annual recommissioning

HTM 02-01 asks for annual recommissioning for patient and staff safety, at intervals no greater than 12 months: the whole system is shut down, recommissioned and cleaned (19.172 to 19.175).

Pumps: isolate the plant electrically (both pumps on a duplex), strip and clean the balance valves and refit them fully open, and clean or replace the internal pump filters and silencers.
Terminal units: strip the second-fix units, clean the adjustable bobbins and reassemble them fully open.
Set-up: with power restored and the alarms checked, close the balance valve gradually at the pump test point until the pressure reaches about 10 kPa, then check and record each terminal unit's flow and set it to the lowest flow for the system, for example 50 L/min or 80 L/min. The aim is the lowest system pressure with the terminal units fully open.
PIR or ventilation control: prove the control and set the overrun to at least 30 minutes.
Full system check: all terminal units in use, one per theatre plus the anaesthetic room where there is one; in radiology no diversity is allowed.

Between recommissionings the balance valve is checked and cleaned of debris weekly (12.7), and a full recommissioning follows any pump replacement (12.26).

ULTRASEG

ULTRASEG terminal units have an adjustable orifice to set the flow. The ULTRASEG datasheet describes routine maintenance as an annual operating inspection and, if needed, replacement of the protective filter element.