Local Application Systems

LOCAL APPLICATION SYSTEMS Local application systems are used to protect hazards, such as oil-filled transformers and paint dip tanks. Ventilating fans, conveyors, flammable liquid pumps and mixers associated with the operation may be interlocked to shut down automatically when the protection system is activated. A typical arrangement of a local application carbon dioxide system is shown in figure 8-34. HALOGENATED GAS SYSTEMS Several types of halogenated gas systems have been developed for fire protection purposes: Halon 104, Halon 1001, Halon 1011, Halon 1202, Halon 1211, Halon 1301, and Halon 2402. The numbers relate to the chemical formulas of the gases. The first digit identifies the number of carbon atoms in the chemical molecule; the second digit identifies the number of fluorine atoms; the third digit identifies the number of chlorine atoms; the fourth digit identifies the number of bromine atoms; and a fifth digit, if any, identifies the number of iodine atoms present. Primarily, Halon 1301 and Halon 1211 are in general use in the United States today. These two types are recognized by the National Fire Protection Association (NFPA). Standards for their installation and use are published in the National Fire Codes. Halogenated gas systems are used in the following situations: l A clean extinguishing agent is needed. l Energized electrical or electronic circuits are to be protected. Figure 8-34.—Local application carbon dioxide system installation. 8-28