Protection against gas.
A gas is referred to as an ideal gas when its molecules can move about individually without restraint. Due to its total mobility, gas is compressible. Its volume depends on the surrounding pressure.
Unlike a liquid, a gas does not have one particular volume. It spreads out completely and evenly in any available space. The transition of liquid to gas is referred to as vaporisation or evaporation; the reverse process is called condensation. The transition of a solid material to gas is called sublimation, the reverse process is known as resublimation.
