A relief valve set to open at a pressure below that at which a container (such as a boiler) would burst
A safety valve is something that allows you to release strong feelings without hurting yourself or others. crying is a natural safety valve
special plug that is connected to a machine or tool and is used to block an opening
a valve in a container in which pressure can build up (as a steam boiler); it opens automatically when the pressure reaches a dangerous level
A safety valve is a device which allows liquids or gases to escape from a machine when the pressure inside it becomes too great. Residents heard an enormous bang as a safety valve on the boiler failed