Inert gas generator (IGG) refers to machinery on board marine product tankers.
[1][2] Diesel is burned using atmospheric air in a combustion chamber and the exhaust gas collected, the resulting exhaust gas contains less than 5% oxygen, thereby creating "inert gas", which mainly consist of nitrogen and partly carbon dioxide.
The hot, dirty gas is then passed through a scrubbing tower which cleans and cools it using seawater.
[1] This generator is sometimes confused with flue gas systems, which draw inert gas from the boiler systems of the ship.
Flue gas systems do not have a burner but only "clean" and measure the air before delivering it to the cargo hold.