Decontamination of halothane from anaesthetic machines achieved by continuous flushing with oxygen.

The contamination of four types of anaesthetic machine with halothane was sequentially sampled by mass spectrometry while the machines were continuously flushed with oxygen 8 litre min-1 for up to 24 h. Contamination decreased in an exponential manner. Machines fitted with Selectatec vaporizer mounting systems and with the vaporizer removed showed contamination less than 0.02 parts per million (p.p.m.) of halothane after 12 h flushing. Machines with cage-mounted vaporizers or with vaporizers left connected to the Selectatec block demonstrated persisting contamination. The Fluotec Mk.4 vaporizer showed an improvement on earlier designs in this respect. Background contamination concentrations of greater than 0.05 p.p.m. were measured in a patient-free recovery area of an operating theatre suite. Concentrations increased to 1 p.p.m. when patients were admitted following halothane anaesthesia. Decontamination of anaesthetic machines to concentrations of halothane below those detected as background contamination within recovery areas may allow such machines to be used safely to anaesthetize patients at risk from halothane.