Elimination of waste anaesthetic gases from operating theatres.

At present, waste anaesthetic gases in the operating theatre are eliminated by room ventilation and by additional measures such as scavenging by a double-mask system and a local exhaust system. A simple technique is proposed for measuring the capture efficiency (E) of different scavenging systems. E is the ratio of the waste anaesthetic gases captured by a system to the total quantity of waste anaesthetic gases produced. In a field study on existing unmodified system, E from a phantom pollutant source was measured using a portable measuring unit designed for displaying test results on location. The pollutant source was a leaking double-mask system. When scavenging from the double-mask system, E was 98% at an exhausted airflow of 28-33 m3/h. Using a local exhaust system at an airflow of 30 m3/h, E ranged from 20 to 96%, depending on the distance between the mask and the nozzle of the exhaust system.