Anaesthetic Gas Scavenging System: How AGSS Protects Theatre Staff

Why waste anaesthetic gas must be removed

Anaesthesia machines release excess gas and vapour through a relief valve and during circuit disconnection or leaks. Without collection, nitrous oxide and volatile agents accumulate in the room air and staff breathe them over a whole working day. Occupational exposure limits and good practice call for control.

A scavenging system collects the waste gas at the breathing system exhaust, transfers it through a connecting hose to a receiving system and disposes of it outside the building. Other measures, such as good ventilation, correct patient masks and leak testing, work alongside it.

Staff awareness matters as much as hardware. Short briefings on leak testing of the breathing circuit, correct mask fit and switching on the AGSS before induction reduce exposure far more than ventilation alone.

Active, passive and the AGSS terminal unit

Passive systems rely on the pressure of the exhaled gas to carry it through ducting, which is simple but sensitive to resistance and wind. Active systems use a vacuum or fan source to draw waste gas away, controlled so that it does not apply suction to the patient's breathing circuit. Active scavenging is the usual approach in modern theatres.

In a piped active system, the AGSS terminal unit on the theatre wall or pendant is the point where the hose connects. It has a gas-specific connector, so it cannot be confused with oxygen or medical air, and is linked to the disposal plant. The receiving system provides a safety buffer between the anaesthesia circuit and the vacuum or fan.

• Collection at the breathing system exhaust
• Transfer hose with the correct connector
• Receiving system that protects the circuit
• Disposal plant venting outside the building

Components of a piped AGSS

A piped AGSS consists of terminal units, dedicated pipework, a disposal source such as a vacuum pump or fan set, controls and alarms, and a discharge to a safe outdoor location. Discharge must be away from air intakes, windows and public areas.

The pipework and the plant are separate from the medical vacuum system, because the flows, materials and risks differ. Standards for AGSS, including the relevant part of the ISO 7396 series, describe requirements for performance, discharge and testing; confirm which edition applies to your project. For general pipeline background see medical gas pipeline components.

Design and operating points

Plan terminal unit positions near each anaesthesia machine, allow for the hose length and avoid trailing hoses across walkways. Size the disposal plant for the number of simultaneous rooms, with duplicate units and alarms to show if the system is not working. Keep the discharge point clear and clearly labelled.

Check that the connecting hose is not kinked, that the receiving system is intact and that the AGSS is switched on before the case. Avoid confusing AGSS with suction. The two systems have different connectors and functions; for suction design see medical vacuum system design.

Testing, maintenance and what to ask a supplier

Test the flow at terminals, the alarm function and the discharge, and include the system in the planned preventive maintenance with your pipeline, as in medical gas pipeline maintenance. Anaesthetists should report any smell or sign that scavenging is not working.

When specifying, ask for the performance data of the disposal plant, terminal connector standard, alarm integration and documentation. Beckfinity can advise on theatre gas and pendant solutions; contact our specialists to discuss your operating rooms.