| Abstract | In recent years, with the halon phase-out, there has been a major thrust towards finding new advanced fire suppression systems. Some of the newly developed fire suppression systems include halocarbon and inert gaseous agents, water mist systems, compressed-air-foam systems, and aerosol and gas generators. Halocarbon agents are chemicals similar to halon except that its molecular structure was modified to reduce or eliminate the chlorine and bromine atoms that are responsible for ozone depletion. They can extinguish fires at their design concentration, however, they produce Thermal Decomposition Products (TDP) including hydrogen fluoride (HF) at much higher levels than halon. Inert gas agents extinguish fire by oxygen depletion. They have zero ODP and no Global Warming potential, and they are not subject to thermal decomposition when used in extinguishing fires. However, they require high-pressure storage cylinders which has implications for space and weight. Fire suppression by water mist is mainly by a physical mechanism. Water mist fire suppression systems have demonstrated a number of advantages, such as good fire suppression capability, no environmental impact and no toxicity. However, water mist does not behave like a total flooding agent, thus the fire suppression effectiveness of water mist depends on the potential size of the fire, properties of the combustibles, and the degree of obstruction, as well as the water mist characteristics. Aerosol systems produce micron size dry chemical particles and gas products, and extinguish fires by removing and recombining flame propagation radicals and by absorbing heat. Gas generators produce a large quantity of inert gases by combustion of solid propellants, and extinguish fires by oxygen depletion. All of the recently developed fire suppression systems extinguish fires at their design conditions, however, no one system can be chosen as the best system for all applications. Some perform better than others in a particular application. All have some limitations and concerns that have to be dealt with in extinguishing fires. |
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