The incendium grenade is a splash damage-type weapon that can be acquired in Barotrauma.
When tossed, the incendium grenade will detonate upon making contact with any entity, signified by a bright flash. It will then generate a large amount of fire in the surrounding area, as well as burning any player or creature within its area of effect. It is recommended to only use the grenade whenever a creature enters the submarine and is at a relatively far distance from the player. It is best to have a Fire Extinguisher nearby whenever the grenade is used.
An incendium grenade requires one hand to use. Once equipped, the player can hold down right-click (mouse2) to aim the grenade. The player's arm will then angle itself in whatever direction your cursor is currently positioned at. Left-clicking (mouse1) will then toss the grenade in the given direction.