Pressure relief valve (medical gas line)

On manifolds, each pressure safety valve should have a flow capacity at least equal to that of the upstream regulator, and its discharge should be vented outside the building where it will not present a fire hazard or cause injury. On medical air plant, valves on each compressor delivery should be capable of discharging the compressor's total throughput, and those immediately downstream of each regulator the system demand flow; these safety valves should conform to BS EN ISO 4126-1 and be of the closed-bonnet type. In dental air pipework, valves protecting distribution pipework should lift at 10% above nominal line pressure.

For manifolds, only individually tested and certificated pressure safety valves should be used; they should not be tested on site but replaced within five years of their stamped test date. The line relief device should be connected by a three-way cock so it can be exchanged for a certificated replacement. Part B says it is not appropriate to test the system by raising the line regulator setting or manually unseating the relief valve, as anaesthetic equipment could fail. See why pipelines need relief valves.