TOTAL FLOODING SYSTEMS

Total flooding systems are used for rooms, ovens, enclosed machines, and other enclosed spaces containing materials extinguishable by carbon dioxide.

For effective total flooding, the space must be reasonably well enclosed. Openings must be arranged to close automatically and ventilation equipment to shut down automatically, no later than the start of the discharge. Otherwise, additional carbon dioxide must be provided to compensate for the leakage.

Automatic closing devices for openings must be able to overcome the discharge pressure of the carbon dioxide. Conveyors, flammable liquid pumps, and mixers associated with an operation may be arranged to shut down automatically on actuation of the protection system. A typical arrangement of a total flooding carbon dioxide system is shown in figure 8-33.

Figure 8-33.-Total flooding carbon dioxide system installation. 8-27

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.

. Flammable liquids or flammable gases are present.

l Surface-burning combustible solids are to be protected.

. For high value objects or processes.

. The area to be protected is occupied by people.

. Availability of water or space for other types of systems is limited.

Generally, Halon 1211 and Halon 1301 are used in total flooding applications.

For effective fire-fighting purposes, a minimum concentration of 5 percent is recommended for total flooding systems for surface fires of ordinary combustibles. Deep-seated fires, as in cable insulation, require much larger concentrations and extended holding times.

Halon 1211 is toxic to people when concentrations exceed 4 percent. This prevents its use as a total flooding agent for areas occupied by personnel. Halon 1211 is normally used in portable extinguishers because it is not in enough concentration to be a hazard for people. Equipment for halon fire extinguishing systems is similar to that used for high-pressure carbon dioxide systems. Halon 1301 is stored in a cylinder super pressurized with nitrogen to 600 psi (at 70F) to provide an expellant pressure for the agent in excess of the agent's normal vapor pressure.

Because of the high ozone depletion factor of halons, installation of new Halon 1301 systems are prohibited except by special approval from NAVFACENGCOM.

Halon 1301 is the least toxic of the halongenated gases and does not harm personnel when concentrations are below 10 percent. Systems that remain in use are located in computer rooms.

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