Evaluation of the efficacy of an active scavenger for controlling air contamination in an operating theatre.

Contamination of the air with halothane in a poorly ventilated ENT theatre was found to be very great (median concentration 449 micrograms litre-1, 177 samples), but was reduced significantly (P less than 0.005) by the use of an active scavenger of patients' expired gases (median concentration 159 micrograms litre-1, 168 samples). For about 18% of the time when the theatre was in use, the halothane concentration in the air was greater than 1000 micrograms litre-1, whether or not the patients' expired gases were being scavenged. Although not measured quantitatively, this appeared to correspond approximately to the period of time in theatre when patients were not connected to the anaesthetic circuit.