Starting A Fire
There are several ways to start a fire. The first is with a molotov cocktail, which will shatter and spread fire in a short radius around the impact point.
The second way to start a fire is with the flamethrower. It spews out a jet of flame directly in front of you, igniting all it touches.
Finally, players can use ammo stockpiles or explosive barrels to start fires, if said items are near any vegetation. Explosions are also caused when players drive a damaged vehicle for too long, but beware; the flames can easily spread to the driver of the vehicle as well.