Inadvertent contamination of anaesthetic circuits with halothane.

All halothane vaporizers tested for leakage when turned off, leaked significant amounts of halothane and this may represent a hazard to patients liable to develop halothane hepatitis or malignant hyperpyrexia. The hazard from leaking vaporizers may be reduced considerably by the use of well-designed bypass units. Circuit contamination by halothane may still result from such sources as neoprene seals around flowmeters, breathing bags and anaesthetic hose which have had previous contact with halothane vapour, whether or not an apparatus is in use. The hazard from contaminated hoses and bags may be reduced considerably by washing and then hanging in a halothane-free atmosphere for a day. The hazard from contamined rubber or plastic components of the anaesthetic machine can be eliminated only by using one apparatus without the vaporizers having been attached at any time during its working life. Similarly, hazards may arise from trichloroethylene vaporizers and from circuit components contaminated with trichloroethylene.