How do theatre staff know that an anaesthetic gas scavenging system has failed?

Under HTM 02-01 (2026), the NHS England guidance, AGSS indicator panels in operating rooms should show green mains on and airflow normal, yellow duty pump failed (plant fault) and red system failed (plant emergency), with the airflow normal indication initiated by a pressure switch or airflow detection device at the pump.

What does the yellow AGSS indicator mean?

In HTM 02-01 (2026), yellow duty pump failed is a plant fault; red system failed is a plant emergency.

Are AGSS alarms tested routinely?

Yes. HTM 02-01 Part B includes indicator and alarm checks in the quarterly AGSS maintenance, and Part A asks for the alarm systems to be checked at commissioning as well.

How do staff know an anaesthetic gas scavenging system has failed?

The indication is part of the AGSS design in chapter 12 of HTM 02-01 Part A (2026 edition):

Indicators should show green mains on, green airflow normal, yellow duty pump failed (a plant fault) and red system failed (a plant emergency) (12.34).
Indicator panels should be installed in operating rooms (12.35).
The airflow normal indication should be initiated by either a pressure switch or an airflow detection device at the pump (12.36).

HTM 02-01 also notes that an AGSS does not have a tertiary supply, so its loss presents a risk of occupational exposure; because AGSS and vacuum systems are fully dependent on the mains electrical supply, a risk-based plan should be in place for them (2.37).

Single-chair dental scavenging

A dental anaesthetic gas scavenging (DAGS) unit should be controlled by a flow switch, have a flow indicator to show that it is running at a specific flow rate, and have an on/off switch on the front with a green LED to show that it is powered (12.43 to 12.45).

How the indications are proven

HTM 02-01 Part B says AGSS maintenance is undertaken quarterly, with annual recommissioning (11.203). Its AGSS task list includes:

confirming the operation of the mains on and running/normal indicators;
on a duplex system, isolating the duty pump and confirming that the standby pump cuts in, which may be accompanied by a pump failure alarm depending on the age and type of the system, then changing over the duty select switch and repeating;
where a low-flow detector is fitted, momentarily disconnecting its feed pipe and confirming that a system failure alarm is given;
checking the alarm indicators in the theatre area as the tests proceed; the system failure alarm may be tested by turning the unit off at the theatre control panel for about 30 seconds, after which switching on should display a system failure indicator that clears within a few seconds, depending on the system;
taking individual flow measurements from all terminal units at both the high and low settings (11.206).

Terminals should be fully dismantled, cleaned and flow tested every year, to coincide with the annual recommissioning (11.205), and at commissioning the user switches, power-on indicators and alarm systems should also be checked (Part A, 19.169). See how an AGSS is tested.

ULTRASEG

ULTRASEG has a modular construction that keeps one pump in operation while the other is on standby or in maintenance, and in automatic mode it allows turnover between the pumps. The datasheet states that its electrical control box meets the ISO 7396-2 requirements for anaesthetic gas suction systems, and supplementary information for a building management system, or remote information, is available as an option.