Firefighting
Open air fire

For outdoor fires, the seat of the fire is sprayed with a straight spray: the cooling effect immediately follows the "asphyxia" caused by vaporization and reduces the further amount of water required. This is because water droplets, upon forming in to water mist, increase their surface area by a large magnitude, greatly increasing the endothermic cooling effect and robbing the fire of oxygen. A straight spray is used so the water arrives massively to the seat of the fire before it vaporizes. A strong spray may also have a mechanical effect; it can disperse the combustible product and thus prevent the fire from starting again. Spray is always aimed at a surface or an object. For this reason, the strategy is sometimes called a two-dimensional or 2D attack.

An outdoor fire is always fed with air, and the risk to people is limited as they can move away from it, except in the case of wildfires or bushfires where they risk being easily surrounded by the flames. It might, however, be necessary to protect specific objects like houses or gas tanks against infrared radiation, and thus to use a diffused spray between the fire and the object. Breathing apparatus is often required as there is still the risk of inhaling smoke or poisonous gases.
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