Early and late scavenging of anaesthetic gases.

The effectiveness of two waste gas scavenger devices, the Carstens box and the Ventex apparatus, with regard to nitrous oxide pollution was studied under comparable conditions in an operating theatre. The scavengers were brought into use in the early and late stages of induction of anesthesia, and nitrous oxide concentrations in the breathing zone and theatre peripheral air were measured. Both scavengers reduced nitrous oxide pollution at the sampling points. Similar reductions in nitrous oxide pollution in the breathing zone were obtained with both scavengers, but the Carstens box was more effective in reducing nitrous oxide pollution in the peripheral air.