[Art]

If you've ever watched professional Oil Well Drillers, if an oil rig ever catches fire, there's usually only one proven method to extinguish that fire...through the use of something to quickly evacuate the oxygen from the area, much like what Ultron mentioned...Explosives!!

Yes, for years a man named Red Adair, Firefighter with the knowledge and expertise to snuff the flames of countless fires during his career.

The explosion requires a large amount of oxygen in order to combust, more than the fire, thus the fire becomes temporarily starved of oxygen for those few precious moments and can no longer support itself.
Read more about Red here:

http://www.manythings.org/voa/people/Red_Adair.html

[ranch vermin]

thats amazing i never thought of that.

[Ultron]

Yes that I suppose works... All of these methods involve either cooling the hotspot or, more frequently - taking the oxygen away from the reactants. Explosions are one way, but sadly very limited - cannot be used if there is expensive equipment or people trapped nearby and it would take an explosion with a yield parallel to that of a nuke (except I am not sure if an atomic bomb would work as it is not a classical combustive exothermic reaction) to stop a forest fire - while still not saving the forest and it's integrity.

[Art]

Smokey the bear always said, "Only YOU can prevent forest fires!"

Fighting them once they've started is another issue best left to the fire rangers, helicopters, water carriers and other technology at their disposal.
Smoke Jumpers as they're called. Dangerous business indeed!