Fire protection systems are installed in every building as a basic precaution according to the building laws and codes prevalent on such construction. Fire extinguishers form an integral part of active fire protection process and are composed of various chemical solutions to treat different genres of fire.
The use of fire extinguishers based on fire classes
The type of fire extinguisher used is dependant on the source point of the ignition and the materials present in the environment. Fires are classified by alphabets according to the source or the cause.
There are mainly five classes of fire. Class A deals with dry combustion agents such as cloth, wood, paper, rubber and plastic. This type of fire can be put out with the help of water fire extinguishers, applied under high pressure.
Class B fire is caused by flammable liquids exclusive of cooking oils and animal fats, petrol, gasoline and paint. Class C deals with gaseous sources of fire such as hydrogen. Class D is a modification of Class B that deals with fire caused by cooking agents such as vegetable oils and animal fats. All these classes of fire should be extinguished with the help of dry fire extinguishers composed of any one of potassium carbonate, carbon dioxide or ammonium phosphate.
Metallic fires are classified as class K in America and Class F in Australia and Europe. Metals such as magnesium, potassium and sodium cause them. Although electricity itself does not burn, the presence of live current in the middle of a fire can aggravate the situation or cause inhibitions in the extinguishing process.
Fires caused by metals must be extinguished with dry agents instead of wet ones due to the risk of the latter reacting with the former and aggravating the combustion process.
Ammonium phosphate can be used for classes A, B and C fires. It is also very corrosive on metals since it forms phosphoric acid, which eats into the surface. However, potassium carbonate can be used only for B and C. all these factors must be kept in mind while installing fire extinguishers in a building. It is obvious from such information that buildings that have too many electronic devices should not have dry extinguishers for use. Therefore, carbon dioxide extinguishers are preferred for such areas. They also do not leave behind any residue on the surface on which they are applied, unlike dry extinguishers. However, carbon dioxide extinguishers cannot put out class A fires. In fact it helps in reigniting them.