Bellows Relief Valve

relief valve
The relief valve (RV) is a type of valve used to control or limit the pressure in a system or vessel which can build up by a process upset, instrument or equipment failure, or fire.
Used at the discharge of a positive displacement pump. An adjustable, spring-loaded valve opens when a preset pressure is reached. Used to prevent excessive pressure buildup that could damage the pump or motor.
safety valve: 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

bellows
In photography, a bellows is the pleated expandable part of a camera, usually a large or medium format camera, to allow the lens to be moved with respect to the focal plane for focusing.
A kind used in a harmonium or small organ
a mechanical device that blows a strong current of air; used to make a fire burn more fiercely or to sound a musical instrument
A bellows is a device for delivering pressurized air in a controlled quantity to a controlled location. Basically, a bellows is a deformable container which has an outlet nozzle. When the volume of the bellows is decreased, the air escapes through the outlet.
A kind with two handles used for blowing air at a fire
A device with a bag that emits a stream of air when squeezed