Introduction to anaesthetic vaporisers

The purpose of an anaesthetic vaporiser is to produce a controlled and predictable concentration of anaesthetic vapour in the carrier gas passing through the vaporiser.
Most vaporisers are of the plenum type, which consists of a vaporising chamber containing the liquid anaesthetic, and a bypass. Gas passing through the vaporising chamber volatilises the anaesthetic and is then mixed with the anaesthetic-free gas bypassing the chamber, the proportion of vapour-containing gas and bypass gas being controlled by a tap.

(Latin plenum (spatium), full (space), neuter of plenus)