Overfill testing of anaesthetic vaporizers

We tested six anaesthetic vaporizers with keyed filler adaptors to see if it was possible to overfill them. For those vaporizers which could be overfilled, the maximum level of overfill was determined and the effect of overfilling on the vaporizer output concentration was measured. Three of the vaporizers, the TEC 4, PPV Mk 1 and MIE Vapamasta 5, could be overfilled. In the case of the TEC 4 and PPV vaporizers, overfilling by more than 100 ml caused a large increase in the vaporizer output concentration. Overfilling the Vapamasta 5 by this amount caused the output concentration to decrease.