Fixed Carbon Dioxide Fire Extinguishing System (Marine CO2 System)is probably the most popular of all the fixed fire-fighting systems employed at sea. The normal design incorporates a fixed bank of CO2 container bottles whose contents can be directed, automatically or by direct manual operation, into any of the ship’s protected spaces. Many systems are used in conjunction with a smoke detector unit, the same sampling pipes guarding against smoke being used to inject the CO2 gas via a three-way valve.

Fire-fighters should be aware that CO2 is a smothering agent rather than an actual extinguishing one. The purpose of the gas is to deprive the fire of oxygen and by so doing break the fire triangle. Carbon dioxide is heavier than air and is usually injected into the upper levels of cargo holds and machinery spaces, all the oxygen being pushed to the upper levels as the CO2 settles at the bottom of the space.

CO2 gas has the following characteristics:

1.It is a non-flammable gas.
2.It is colourless.
3.It is odourless.
4.It is readily available in almost every port of the world.
5.It is comparatively cheap compared, say, to Halon.
6.Systems may incorporate smoke detector units.
7.It may be kept either in 45 kg cylinders or in bulk storage tanks.
8.Normal temperature of liquefied CO2 is -20℃。