For low, slow fires like grass fires, it does not have to be water. Watery foam with bubbles of CO2 or another fire-inert gas can work well for smothering the f

For low, slow fires like grass fires, it does not have to be water. Watery foam with bubbles of CO2 or another fire-inert gas can work well for smothering the fire. But the equipment to make foam properly is expensive and finicky and not all fire departments have it. And foam won't help much as a heat sink which is where water really shines. Heat sinks are what you need for big fires. Lots and lots of water. Forest fires are never put out with water--you just can't get enough water where it's needed. Instead, you use small amounts of air-dropped water and fire breaks to steer the fire where you want it to go and let it run out of fuel.