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Chemical foam is a stable solution of small bubbles containing carbon dioxide with lower density than oil or water, and exhibits persistence for covering flat surfaces. Because it is lighter than the burning liquid, it flows freely over the liquid surface and extinguishes the fire by a smothering (removal/prevention of oxygen) action.
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.
Fire is the rapid oxidation of a material (the fuel) in the exothermic chemical process of combustion, releasing heat, light, and various reaction products. [ 1 ] [ a ] At a certain point in the combustion reaction, called the ignition point, flames are produced.
Arguably the first chemical reaction used in a controlled manner was fire.However, for millennia fire was seen simply as a mystical force that could transform one substance into another (burning wood, or boiling water) while producing heat and light.
Fire making, fire lighting or fire craft is the process of artificially starting a fire. It requires completing the fire triangle , usually by heating tinder above its autoignition temperature . Fire is an essential tool for human survival and the use of fire was important in early human cultural history since the Lower Paleolithic .
Dry chemical powder is used on all classes of fires. Dry chemical powder puts out the fire by coating the burning material with a thin layer of dust, thereby separating the fuel from the oxygen in the air. The powder also works to interrupt the chemical reaction of fire, so these extinguishers are extremely effective at putting out the fire.
In a 1988 test program, conducted by the former National Bureau of Standards (NBS), now the National Institute of Standards and Technology (NIST), to quantify the effects of fire retardant chemicals on total fire hazard. Five different types of products, each made from a different type of plastic were used.
Gaseous fire suppression, also called clean agent fire suppression, is the use of inert gases and chemical agents to extinguish a fire. These agents are governed by the National Fire Protection Association (NFPA) Standard for Clean Agent Fire Extinguishing Systems – NFPA 2001 in the US, with different standards and regulations elsewhere.