(1) Cooling and extinguishing
Once combustibles reach the ignition point, they will burn or continue to burn. Under certain conditions, if the temperature of the combustibles drops below the ignition point, the combustion will stop. For combustible solids, cooling them below the ignition point; for flammable liquids, cooling them below the flashpoint, the combustion reaction may stop. The use of water to extinguish fires caused by general solid materials is mainly achieved through cooling. Water has a large specific heat capacity and a high heat of vaporization, and the cooling performance is very good. In the process of extinguishing fire with water, the water absorbs a large amount of heat, so that the temperature of the burning material is rapidly reduced, the flame is extinguished, the fire is controlled, and the fire is terminated. The water mist of the water spray fire extinguishing system has a small diameter of water droplets, a large specific surface area, and a large contact area with the air. It can easily absorb the heat of the hot airflow, and can also quickly reduce the temperature, and the effect is more obvious.
(2) Isolation and fire fighting
Among the three elements of combustion, combustibles are the main factor of combustion. Separating combustibles from oxygen and flames can stop burning and extinguish fires. For example, the automatic water spray-foam combination system sprays foam while spraying water. The foam covers the surface of the burning liquid or solid, and while cooling the surface, it separates combustibles from the air, so as to extinguish the fire. For another example, when extinguishing a flammable liquid or combustible gas fire, quickly close the valve that transports combustible liquid or combustible gas, cut off the combustible liquid or combustible gas pipeline flowing to the fire area, and open the combustible liquid or combustible gas to a safe area at the same time The valve can transfer the combustible liquid and combustible gas in the container that is already burning or about to burn or is threatened by fire.
(3) Suffocating and extinguishing the fire
The combustion of combustibles is oxidation, and it needs to be above the minimum oxygen concentration. If it is below the minimum oxygen concentration, the combustion cannot proceed, and the fire is extinguished. Generally, when the oxygen concentration is lower than 15%, combustion cannot be maintained. In the fireplace, the oxygen concentration in the space can be reduced by filling non-combustible gas, such as carbon dioxide, nitrogen, steam, etc., so as to achieve suffocation and extinguishment. In addition, when the water spray fire extinguishing system works, the sprayed water droplets absorb the heat of the hot air flow and convert it into steam. When the water vapor concentration in the air reaches 35%, the combustion stops. This is also the application of suffocation fire extinguishing.
(4) Chemical suppression to extinguish the fire
Since flaming combustion is carried out through a chain reaction, if the generation of free radicals can be effectively suppressed or the concentration of free radicals in the flame can be reduced, the combustion can be stopped. The common fire extinguishing agents for chemical suppression fire extinguishing are dry powder fire extinguishing agent and heptafluoropropane fire extinguishing agent. Chemical suppression is fast to extinguish fires, and when used properly, it can effectively extinguish the initial fire, reducing casualties and property losses. This method is effective for flaming fires, but for deep fires due to poor permeability, the extinguishing effect is not ideal. Where conditions permit, the use of chemically suppressed fire extinguishing agents in combination with water, foam and other fire extinguishing agents will achieve significant results.
