Things that causes fire
- Incendiary launcher
- Molotov Cocktail
Sparks from a fire causes another fire if they land on something burnable. (Unconfirmed: is it 100% chance that a fire will start if this happen or is it a chance that it happens?)
By Using Explosions
Fires that are caught in the explosion of a blasting charge are extinguished, haven't tested with frag grenades yet.
Like in a crematory
Plants burn, Molotov cocktails are good to start fires, just don't burn down your base.