Halon an extinguishing agent was developed after World War II for the protection of aircraft engines. Several types were developed, and several were banned and discontinued such as halon 104. Other types were halon 1202, halon 1211, halon 1301, and halon 2402, which was never widely used in the United States due to its high toxicological concerns. Halon type 1101 was widely utilized for aircraft engines. The two most common types being; halon 1301 bromotrifluoromethane, CBrF3, which is most commonly used in fixed system, and halon 1211 bromochlorodifluoromethane, CBrClF2, which is used in portable systems. Halons are synthetic gases, grouped under the category of halogenated hydrocarbons, that exhibit exceptional fire-fighting and explosion prevention/suppression effectiveness when appropriately applied. Halon chemically interferes with the combustion process of fire resulting in extinguishment. Halon is stored as a liquid, which then vaporizes into a gas. Its boiling point is negative 72 degrees Fahrenheit. Halon in non-conductive and non-toxic when used at 5 7 percent concentrations.
Even though it is non-toxic human exposure should be less then 15 minutes when concentration is 0 7 percent. With a higher concentration 7 15 percent exposure should be less than one minute. Fire fighters should wear full protective gear and SCBAs when exposed to halon. Halon is considered a clean agent it leaves no residue behind and does not cause any damage to the applied area. Halon is used in computer rooms to safely extinguish any fire that may happen so that minimal damage will be caused. Computer rooms that contain millions of dollars worth of equipment. Hitachi Data Systems main computer room in Santa Clara of Lafayette and Central is one example. This room contains millions of dollars worth of computers. There is more computer power in this room than any other in the United States. It is protected by a halon 1301 fixed system, and several halon 1211 type extinguishers.
Halon is also the best extinguishing agent for flammable liquids. In a flooded type halon system concentration should reach 5 percent concentration in 10 seconds. During tests halon has put out a flammable liquid fire with a 20-minute pre-burn time with a concentration of 5.6 percent. Every fixed halon system must contain a storage vessel, which is where the halon is contained in a liquid form. A piping system to deliver the agent to the nozzles which is where the halon turns into its vapor form. Ionization type detection system. Two alarms must be set of before it is discharged. The second one is to confirm. An abort switch to cancel the discharge. A manual pull station that will override everything. A pre-alarm bell to warn that halon will be released in the area. Warning signs must also be placed on the entrances to the room. Also the abort switches and the manual pull stations are placed at every exit of the room. In most cases there is also an exhaust fan to clear the room out after a release has occurred.
Although halon has become a great fire suppression system since its initial use, it has now become illegal to manufacture in the United States. It was discovered in the early 1980’s that certain man-made chemicals depleted the Ozone Layer. Among Ozone Depleting Substances (ODS) are methyl bromide which is contained in halon. The Montreal Protocol is an international agreement by over 140 member countries to eliminate the production of ODS in order to protect the Earth’s Ozone Layer. Therefore, halon production in the United States ended on December 31, 1993 because it contributes to depletion of the ozone layer. They cause ozone depletion because they contain bromine. Bromine is greatly more effective at destroying ozone than chlorine.
The end of halon production has had a dramatic impact on the protection of special hazards against fire and explosion. However, halon systems are still being used today and it is not illegal to use the agent itself. The halon supply in the United States is said to be enough to last for 50 years or more. Halon is also smuggled across the border from Mexico, keeping the halon supply high. There are new safer alternatives to halon, but replacing there many applications still prove to be a challenge. The new agents are also more expensive. Hitachis computer room in Indian used the agent FM 200 that cost around 50,000 dollars just for the chemical in a much smaller room.
Apple Computers also used the FM 200 agent in their recently remodeled server room, in Cupertino. The system was halon before the remodel took place but was changed during the remodel. The components for the system are basically the same with the; warning signs, pre-alarm, storage unit, piping system, nozzles which are a little different, abort switch, and the manual pull stations. Another problem with these alternatives is that there needs to be a greater amount of agent released to acquire the same effect as halon. But FM 200 has zero ozone depletion, zero global warming, and zero atmospheric lifetime.
While FM 200 replaces the halon for fixed systems FE-36 replaces the halon in portable fire extinguishers. Other halon substitutes are FE-13, FE-25, and FE-241 all manufactured by DuPont. Halon is slowly being replaced by new and safer alternatives, but it will not be done completely until the supply of halon runs out. The new agents still have limitations compared to halon eventually it will happen. There are lots of new agents on the market right now all saying that they are better than the other, but still cant meet the wide range of uses that halon can.