Fire Retardants

substances or mixtures protecting wood, textiles, and other materials of organic origin from ignition or spontaneous combustion. The protective action of fire retardants is a result of several factors. They have a low melting point and form an airtight film that bars oxygen from the protected material. They decompose under heat and produce inert gases or vapors which hinder the ignition of gaseous products formed by the decomposition of the protected material. They absorb large quantities of heat during the melting, evaporation, and dissociation of the antioxidant, thus preventing the treated material from reaching its own decomposition temperature. They increase carbon formation by the treated materials during decomposition by generating acids.

The most widely used fire retardants are ammonium phosphates (diammonium phosphate, monoammonium phosphate and mixtures of the two), ammonium sulphate, borax, and boric acid; ammonium chloride and zinc chloride are used less often for this purpose.

Materials are made fire-retardant by deep permeation with aqueous solutions (50–66 kg of anhydrous salt per cubic meter of wood) and then drying. In addition, fire-retardant coatings are applied to surfaces in the form of solutions (DSK-P, made of diammonium phosphate, ammonium sulphate, and a kerosene catalyst; PPL, based on potash and a kerosene catalyst; and others), paints (FAM, a furfural-acetone blend with an admixture of ureaformaldehyde resin; PCVO, based on chlorinated polyvinyl chloride resin; and MCS, an oil paint with chloroparaffin and other components), and caulking compounds (made from superphosphate, clay and limestone, and so on). Those parts of equipment subject to outdoor exposure are further treated with weatherproof fire-retardant paint.