Anaesthetic machine pipeline inlet pressure gauges do not always measure pipeline pressure.

Some anaesthetic gas machines have pipeline inlet pressure gauges which indicate the higher of either pipeline pressure, or machine circuit pressure (the pressure distal to the pressure reducing valve, and proximal to the flowmeter control valve). Failure by the operator to appreciate this feature may in specific circumstances lead to a delayed appreciation of pipeline malfunction or disconnection. The Canadian Standards Association Z168.3-M1980 Anaesthetic Gas Machine Standard requires pipeline inlet gauges which measure only pipeline (hose) pressure. Existing machines should be modified to accommodate this requirement.