Document 2B5o3aZKmV905jMkvvOYmwEp

Fir 36-9 -- Proportioner permits operator to varv percentage of foam-producing concentrate are listed by Underwriters' Laboratories, Inc , are siphoned through a proportioner at rates not exceeding 2 per cent by volume The reflective white opaque surface formed by the air bubbles and wet-water particles makes this agent a good medium for protec tion from exposure fires The cellular struc ture of the foam also retards heat conduction, thus affording insulation As the foam blanket absorbs the heat and breaks down, the wet water released from the air bubbles car ries the heat away from the protected surface Mixing wetting agents with other wetting agents or with mechanical or chemical foam is not recommended, since it may neutralize the effect of the agents and thus destroy the fire fighting properties High expansion foam, using wetting agents in ratios as high as 1000 to 1, has been devel oped These foams have a water content ranging from 0 2 to 10 oz/cu ft, and are effec tive in fighting fires in inaccessible places, such as coal mines and building basements High expansion foams can also be used in total flooding systems designed to fill en closed spaces, such as rooms or buildings The systems are suitable for hazards involv ing flammable liquids and ordinary combus tibles, if properly designed for the specific hazard and area Wet water The wet water principle can also be used without generating foam In liquid form, wet water has the same general extinguishing properties as plain water However, its cool ing ability is increased, and there is a greater penetration of porous surfaces because of its reduced surface tension Carbon dioxide extinguishing systems Fixed (local or flood-type) C02 systems are often installed for the protection of rooms that contain electrical equipment, flammable liquid or gas processes, dry cleaning machin ery, and other exposures where fire can be ex tinguished by diluting the oxygen content of the air or where water must not be used be cause of electrical hazard or the nature of the 1089