The uncontrolled fire is terrible for the man. In the primitive housings of other times and in the packed shanties of the old cities, a fire used to have catastrophic effects; in 1666 a great fire destroyed fourth three parts of London, the fire disappeared the city in four days. Thirteen thousand houses were destroyed and the only possibility to reduce the fire was to demolish houses to form against fires among the crowded ones. The fire in certain way, constituted a reparation, since the reconstruction was made with brick that is incombustible. It was until the XIX century that the firemen, a professional entity dedicated to the extinction of fires, was organized.

The fires of forests are the most difficult of combatting. To avoid them, due to the great value of the losses in a fire of this type, it has been proceeded to a continuous surveillance of forests, from airplanes and discharges towers, mainly during the summer. The fire of a forest, in flat land, is easier of dominating that in uneven land, where the fire spreads with more speed. In the fire of a forest fire walls settle down before the front of the fire, in perpendicular sense to the direction of the wind, being eliminated from the burning land all combustible vegetation. The extinguisher patrool mounts the watch in the external part of the fire wall and it attacks the fire with hoses of water.

In the fires of buildings, often is necessary to save human lives. The firemen have stairways of up to 50 m. of height to evacuate people threatened by the Flames. They have canvases likewise on those that people in danger can jump without risk. If there are several houses in Flames, they proceed firstly to the extinction of the fire in a indirect form: it is tried to impede its propagation throwing water on the surrounding properties.

The automatic alarm for fires can work by diverse sensitive devices that react before the smoke, the light, or the heat. The smoke detector gives the alarm when the gases of the fire penetrate in its ionization camera. The flame detector has a photoccell that reacts before the fire's infrared light. The thermal detector its constituted by two metallic twigs that melt at 158 °F and give the alarm sign. The alarm can also activate a device that, from a pipe in the ceiling shoots presurized water or carbonic acid (HCO₃).

A fire is combatted suppressing anyone of the three essential conditions for fire exists. It can be impeded the oxygen excess, for example with the help of a blanket; or tossing water on the the fire's source to cool it and this way to take its temperature under the ignition point; or, retiring the combustible substances.

With reparation and modernization it has been possible to protect, with more effectiveness, our population's buildings against fire . Devices exist to avoid the propagation of a fire among the adjacent houses. And, on the other hand, construction materials like the stone and the cement offer bigger resistance to fire, what facilitates their extinction.

The danger of a fire exists permanently. Almost every day new inflammable substances are used in the industry and, with the fuels as gas and petroleum, the fire on sometimes comes in explosive form. As I said before on combustion section, an explosive combustion is presented when in a very brief lapse of time a great quantity of fuel burns. This gives as natural consequence that the explosive combustions require a great quantity of oxygen. During this type of quick combustion they are formed and they expand for the heating, a great quantity of gases that produce strong pressures, responsible for the destructive effects of the explosions.