Since time immemorial, man has learned to extinguish a fire with water. But actually, how does it work?
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If water is capable of extinguishing a fireit is thanks to the combination of two effects: suffocation and cooling.
Water smothers fire
To burn, a fire needsoxygen. When we douse a fire withwater, it vaporizes. However, the water vapour tends to take it easy. It can thus occupy several thousand times the volume occupied by the water thrown on the fire. In doing so, it repels the air and therefore the oxygen, and thus suffocates the fire which eventually goes out.
Water cools the hearth
Water also participates in cooling of the fire area. Indeed, when it turns into steam, it absorbs a significant amount of heat. To reach 100°C, 3 liters of cold water consumes 1 megajoule ofenergy. To fully vaporize, these 3 liters will require up to 6 megajoules of energy. This energy being taken from the surrounding environment, prevents the fire from spreading.
Even after the fire is out, it’s always a good idea to keep watering it to cool it down. The installed water vapor can be blown out by the windthe oxygen is then reinstalled and if the embers have remained sufficiently hot, the fire can resume.
Other methods can be used to extinguish the fire, such as the use of fire extinguishers. Their system continues to evolve; there is even a infrasound fire extinguisher.
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