Solid extinguishants

Solid extinguishers such as sand or clay are also used to cover the oil or grease under a fire. They also suppress fire by blanketing. They are suitable for metal fires. Sodium and potassium bicarbonate are also used as solid extinguishers for liquid fuel. They act as chain reaction inhibitors. At high temperatures, they decompose to give carbon dioxide that itself is an extinguisher that suppresses fire. 

When we suppress fires we inhibit their growth and spread. There are various means of fighting and suppressing fires. We will look at five methods of suppressing fires which are isolation, water, gas extinguishants, foams, and solid extinguishants. 

Carbon dioxide is used in the manufacture of sodium carbonate by the ammonia-soda process, urea, salicyclic acid (for aspirin), fire extinguishers and aerated water. Lesser amounts are used to transfer heat generated by an atomic reactor to water and so produce steam and electric power, whilst solid carbon dioxide is used as a refrigerant, a mixture of solid carbon dioxide and alcohol providing a good low-temperature bath (195 K) in which reactions can be carried out in the laboratory. 

It is usually better to use a fire extinguisher charged with carbon dioxide under pressure this produces a spray of solid carbon dioxide upon releasing the pressure intermittently and is effective for extinguishing most fires in the laboratory. 

A.STM. D3801, Test Methodfor Measuring the Comparative Extinguishing Characteristics of Solid Elastics in a Vertical Position Vol. 8.02, ASTM, Philadelphia, Pa., 1987. 

Foam Production This is important in froth-flotation separations in the manufac ture of cellular elastomers, plastics, and glass and in certain special apphcations (e.g., food products, fire extinguishers). Unwanted foam can occur in process columns, in agitated vessels, and in reactors in which a gaseous product is formed it must be avoided, destroyed, or controlled. Berkman and Egloff (Emulsions and Foams, Reinhold, New York, 1941, pp. 112-152) have mentioned that foam is produced only in systems possessing the proper combination of interfacial tension, viscosity, volatihty, and concentration of solute or suspended solids. From the standpoint of gas comminution, foam production requires the creation of small biibbles in a hquid capable of sustaining foam. 

Fire Hazards - Flash Point Not pertinent (combustible solid) Flammable Limits in Air (%) Not pertinent Fire Extinguishing Agents Water, foam Fire Extinguishing Agents Not To Be Used Not pertinent Special Hazards of Combustion Products Toxic oxides of nitrogen may be formed in a fire Behavior in Fire Not pertinent Ignition Temperature Not pertinent Electrical Hazard Not pertinent Burning Rate Not pertinent. 

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