Halon


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 SCBA\'s 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. Hitachi\'s 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