Halon systems

FIra Supprassion Systams 4. 3.1 CO, Systems 4.2.3.2 Water Svstems 4.2.3.3 Dry Powder Systems 4.2.3.4 Halon Systems b. Faulty Indication... 

Halon systems were the ideal fire suppression agent before their implications of environmental impact due to ozone depletion. The industry is gradually phasing out usage of halon systems for this reason. A flowchart to analyze mechanisms to supplement or eliminate Halon systems for electrical or computer processing areas is shown in Figure 11. Some of the prime reasons to eliminate the use of Halon systems is that the facility may be constantly manned with a relatively low fire risk. Other facilities may have a very low combustible load and can be supplemented by highly sensitive fire detection means, such as a VESDA fire detection system. 

Fixed installations, such as water spray systems, halon systems, sprinkler systems, carbon dioxide extinguishing systems, explosion suppression systems, and other fire protection installations are often provided with flow and trouble detection switches connected to transmitters. A signal indicating the condition of the system should be sent to the attended location(s). 

Activation of layers of protection such as relief valves, interlocks, rupture disks, blowdown systems, halon systems, vapor release alarms, and fixed water spray systems... 

Fire protection is another critical safety concern. Automatic fire detectors are located throughout the plant. Sprinkler systems supplied from a large storage tank come on automatically in the event of a fire in the unloading and unpack areas. In other areas, dry chemical systems are deployed. Halon systems protect the control room and power supply room. 

Sprinkler and Halon systems are usually ceiling-mounted, fixed fire-fighting systems. One releases a deluge of water, the other a suppressive gas. Halon systems, which use a gas with the vendor name of Halon, are being phased out because Halon gases are damaging to the ozone layer. 

A major distinction between the use of carbon dioxide as an extinguishing agent and the Halon systems described in earlier sections is that the extinguishing mode for carbon dioxide is primarily simple smothering of the burning fuel, with no chemical action involved. There is tittle cooling action, with an effectiveness for carbon dioxide of about one tenth that of an equivalent amount of water. As a result, once the carbon dioxide has dissipated, the possibility of reignition exists if there are any sufficiently hot areas still present. 

It is clear that far higher concentrations are required than for Halon systems, so high in fact that an individual trapped in a space flooded by the minimum recommended amount of 34% in the table would quickly become unconscious due to lack of oxygen, since in such a case the oxygen concentration would fall to 13.8%. 

Halons Halons are hydrocarbons in which atoms from halogens replace one or more hydrogen atoms. Halons include fluorine, chlorine, bromine, or iodine. There are a variety of halon systems. Extinguishing involves interruption of the hydroxyl radical of combustion. Some systems are discontinued because of toxicity and corrosion effects. Today two halons are in general use Halon 1211 (bromochlorodi-fluoromethane) and Halon 1301 (bromotrifluoromethane). Effectiveness is a function of many factors. Halon 1301 is best suited for total flooding applications, whereas Halon 1211 is weU suited for local application systems. Halon... 

Halon system does not meet tninimum conoealratioaand/OTSoaktimcs,andK-ReaiiOT staad iiiw pfeseetkm does not meet MFPA leqoireineBts. 

A development to replace halon systems has been water mist systems in which a system of open discharge heads is used. The system is actuated by smoke detectors located witiiin the area to be protected. Operation of one detector raises the alarm and it requires a second detector to be actuated before the water is released into the discharge pipework. Water for the system is stored in cylinders at high pressure and the discharge heads are designed to produce a fine water mist. Water mist systems use significantly less water than a sprinkler system and extinguish fires by ... 

Fixed extinguishing systems are seeing increased service. Halon systems previously used for protection of wet benches are no longer available. These systems could protect either the face or the sump of the wet bench. Another common use of Halon was below the raised floor in older fabs. The Halon systems are replaced with FM-200 watermist and CO2... 

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