What method is commonly used for extinguishing structure fires?

Using water or fire retardant foam to cool the flames is a fundamental approach to extinguishing structure fires. This method is effective because it directly reduces the temperature of the burning material below its ignition point, thereby halting the combustion process. Water is a highly efficient coolant and can absorb a significant amount of heat, which helps in rapidly bringing down the fire's temperature. Additionally, fire retardant foam not only cools but also creates a barrier that can prevent the re-ignition of flammable materials by smothering the fire and inhibiting oxygen availability.

The effectiveness of this method lies in the ability of water and foam to penetrate the flames and spread over burning surfaces, providing a comprehensive cooling effect across the fire's area. This is particularly crucial in structure fires, where materials can vary widely and require thorough extinguishing techniques.