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Condensed aerosol fire suppression is a particle-based form of fire extinction similar to gaseous fire suppression or dry chemical fire extinction. The aerosol employs a fire extinguishing agent consisting of very fine solid particles and gaseous matter to extinguish fires. The condensed aerosol microparticles and effluent gases are generated by the exothermic reaction; until discharged from the device, the particles remain in vapor state. They are cooled and "condensed" within the device and discharged as solid particles. To the difference of gaseous suppressants, which emit only gas, and dry chemical suppression agents, which are powder-like particles of a large size (25–150 micrometres), condensed aerosols are defined by the National Fire Protection Association as releasing finely-divided solids of less than 10 micrometres in diameter. The solid particulates have a considerably smaller mass median aerodynamic diameter (MMAD) those of dry chemical suppression agents, remain airborne significantly longer, and leave much less residue within the protected area. Whereas dry chemical systems must be directly aimed at the flame, condensed aerosols are flooding agents and therefore effective regardless of the location and height of the fire. Wet chemical systems, such as the kind generally found in foam extinguishers, must, similarly to dry chemical systems, be sprayed directionally onto the fire. The condensed aerosol agent can be delivered by means of mechanical operation, electric operation, or combined electro-mechanical operation. ==Methods of fire extinction== Condensed aerosol suppressants, like gaseous suppressants, use four methods to extinguish fires. They act on the four elements of the "fire tetrahedron," the disparate components that combine to create the chemical reaction underlying any fire. These four means of fire extinction are: # Reduction or isolation of fuel # Reduction of heat # Reduction or isolation of oxygen # Inhibiting the chain reaction of the above components Condensed aerosols’ primary extinguishing mechanism involves the fourth element of the fire tetrahedron by means of chemical reactions with the free radicals of the flame, therefore interfering with the combustion process of the fire. Typically, condensed aerosol particulates consist of potassium carbonate (K2CO3)) that are produced from the thermal decomposition of a solid aerosol-forming compound that includes potassium nitrate as an oxidizer. As the aerosol particles surround and come into contact with the flame, the particulates absorb the flame heat energy, breaking down and releasing large concentrations of potassium radicals (K+) (ions with an unpaired electron). The potassium radicals bond with the hydroxide (OH+), hydrogen (H+) and oxygen (O+) free radicals which sustain flame's combustion process, producing harmless by-product molecules such as potassium hydroxide (KOH) and water (H2O). K• + OH• = KOH KOH + H• = K• + H2O The potassium radicals are propagated since they are both consumed and produced by reaction with the fire radicals. Disrupting the reactions necessary to sustain the flame's combustion, the cycle continues until the combustion's chain reactions are terminated and the flame is extinguished. Condensed aerosol agents also have secondary extinguishing mechanisms implicating the other three elements of the fire tetrahedron described above. The aerosol cools the flame by engulfing it with a cloud with large concentrations of microparticles which have mass median aerodynamic diameter sizes (MMAD) as small as 1 to 2 micrometres. Though the surface area of each microparticle is extremely small, the large quantity of particles surrounding and penetrating the flame offers a sufficiently large combined surface area to absorb the flame’s heat. On the surface of the particles, recombination of the fire radicals takes place as energy is absorbed: O• + H• = OH• H• + OH• = H20 Flame is the gaseous part of a fire resulting from the combustion of fuel. Aerosols particles and gases mixing with the gaseous components of the flame isolate the fire's fuel. Attacking all the elements of the fire tetrahedron, condensed aerosol fire suppression agents are among the more effective flame-extinguishing agents. For example, some condensed aerosol fire suppressants can extinguish a Class B flammable liquid pool fire with 1/5 the amount of Halon 1301 agent or 1/10 the amount of a hydrofluorocarbon or fluoroketone based clean agent gaseous fire suppression system in terms of kilogram mass of agent per cubic meter. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Condensed aerosol fire suppression」の詳細全文を読む スポンサード リンク
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