A<unk>  is a group of large gas<unk> s, commonly used to supply gases via a pipeline to a building such as a hospital.<unk> s are often arranged into two groups; a primary and secondary group. In a hospital, size J<unk> s are commonly used, which are capable of holding 6800 litres of oxygen each or 13,600 of nitrous oxide. Initially, the gas is used up from the primary group first, with gas being expended equally from all<unk> s, as they are connected in parallel through a common outlet. Once the levels in the<unk> s are sufficiently low, a pressure transducer switches to the secondary<unk> ; allowing the primary<unk>  to be replenished.<unk> s are used to supply nitrous oxide, Entonox, air or oxygen; although a vacuum insulated evaporator is more commonly used to store oxygen. Gas<unk> s should be stored in an area separate from the main building. It should not be exposed to the environment and should be well ventilated.
Cylinder manifold
Hippocratic bench
Needleless connector
Parliamentary snuff box
Carbuncle
Stretcher bearer
Stunt 
Hangnail