Building fires create a tremendous amount of heat and smoke. In many instances, firefighters must remove this heat and smoke before they can get close enough to extinguish the fire. Heat and smoke rise, so cutting a hole in the roof and breaking out windows in strategic locations allows the smoke to vent upwards, allowing cool air to enter the structure from below.
Most fatalities are caused by breathing the smoke and not the flames. This strategy is a lifesaving technique for any occupants. It also improves visibility and lowers heat conditions for the firefighters inside, allowing them to quickly and safely extinguish the fire. Remember, heat and smoke cause damage too, so ventilation will reduce overall damage to a building and contents.