Inert gas system is the most important integrated system for oil tankers for safe operation of the ship.
Inert gas is the gas which contains insufficient oxygen (normally less then 8 %) to suppress combustion of flammable hydrocarbon gases.
Inert gas system spreads the inert gas over the oil cargo hydrocarbon mixture which increases the lower explosion limit LEL (lower concentration at which the vapors can be ignited), simultaneously decreasing the Higher explosion limit HEL (Higher concentration at which vapor explodes). When the concentration reaches around 10 %, an atmosphere is created inside tank in which hydrocarbon vapors cannot burn. The concentration of inert gas is kept around 5% as a safety limit.