Halon.=20 Halon is a halogenated=20 hydro- carbon &nbs= p;in=20 which one or more of the=20 hydrogen atoms have = ;been=20 replaced by atoms from the halogen series (fluorine, chlorine,=20 bromine, or iodine). This= =20 substitution provides nonflammability and=20 flame extinguishing properties. A=20 halon numbering system=20 has been developed to describe <= SPAN=20 class=3Dps15>the various halogenated hydrocarbons. The first=20 digit in the number represe= nts=20 the number of carbo= n=20 atoms in the compound=20 molecule; the second digit, the number of=20 fluorine atoms; the third=20 digit, the number of chlorine atoms;=20 the fourth digit, t= he=20 number of bromine atoms; and the fifth digit, the number of iodine atoms, if=20 any. In this system,=20 terminal zero digits are not expressed. The &nb= sp;two=20 types of halon used aboard=20 Navy ships are Halon 1301 (the=20= most=20 commonly used) and Halon=20 1211, introduced for=20 twin-agent (AFFF/Halon=20 1211) applications on flight and= =20 hangar deck mobile=20 fire-fighting apparatus. Portable Halon 1211=20 extinguishers are also planned for backfit into vital=20 electronics spaces of &nb= sp;all=20 surface combatant ships. Halon 1301 consists of one = atom=20 of carbon, three at= oms=20 of fluorine, no chlorine atoms,=20 one bromine atom, and no=20 iodine atoms. For shipboard installation, Halon=20 1301 is super- pressurized with nitrogen and sto= red=20 in compressed gas=20 cylinders as a liquid. When released,=20 it vaporizes into a= =20 colorless, odorless gas with a=20 den- sity of=20 approximately five times that of=20 air. Halon 1211 con= sists=20 of one atom of carbon, one atom of chlorine, two atoms of fluorine, and=20 one atom of bromine. Halon=20 1211 is also color- less, but it has a sweet smell. Halon 1211 is=20 stored and shipped as &nb= sp;a=20 liquid and pressurized with nitrogen gas. Pressurization is=20 necessary since the vapor=20 pressure is too low to convey it=20 properly to the fire=20 area. The mechanism by which halon=20 extinguishes a fire is not thoroughly= =20 known. However, Halon (1211 and= =20 1301) chemically inhibits the flame=20 front; the halons act by=20 removing the active chemical species involved in the=20 flame=E2=80=99s chain reaction. Halon de= composes=20 upon contact with flames or hot surfa= ces=20 above 900=C2=B0F (482=C2=B0C). Decomposition products=20 are principally hydrogen fluoride=20 and hydrogen=20 bromide. The short=20 discharge time of Halon 1301=20 (10 seconds maximum) keeps the=20 thermal decomposi- tion product= s=20 well below lethal concentrations. The real hazard lies not in the by-products of=20 the halon, but rather in the products= of=20 combustion from the fire.= =20 Products such as CO, combined with the oxygen depletion, heat, and smoke, pose=20 a greater hazard to personnel. Personnel=20 should not remain in a space where Ha= lon=20 1301 has been released to=20 extinguish a fire unless an=20 oxygen breathing apparatus (OBA= ) is=20 worn. If Halon 1301 should=20 inadvertently be released into a=20 space where no fire exists, per= sonnel=20 can be exposed to 5-to-7 percen= t=20 concentrations of Halon 1301 for= =20 up to 10 minutes (depending= =20 upon the individual) without danger to their health.=20 Halon 1301 can be=20 considered a nontoxic and=20 nonsuffocating extinguishing ag= ent in=20 the normal 5-to-7-percent concentrati= ons;=20 however, spaces should=20 be evacuated on=20 halon system discharge. Exposure to Halon 1301 concentrations of up= to about 7 percent by volum= e=20 and Halon 1211 concentrations of 2 to 3 pe= rcent=20 by volume has littl= e=20 noticeable effect on humans. Exposure=20 to Halon 1301=20 concentrations of between 7 and=20 10 percent and Halo= n=20 1211 concentrations of between 3 and 4 percent may cause personnel to experience<= /SPAN>=20 dizziness and tingling of t= he=20 extremities. Those sympto= ms=20 indicate mild anesthesia. At Halon=20 1301 concentrations above 10 percent and=20 Halon 1211 concentrations = ;above=20 4 and 5 percent, the dizziness becomes pronounced. Subjects=20 feel as if they=20 will lose consciousness (although=20 none have), and phy= sical=20 and mental dexterity is reduced. No significant adverse health effects=20 have been reported from=20 the use of Halon 1301 or=20 1211 as a fire=20 extinguisher since their introduction=20 into the marketplace. Direct contact with vaporizing li= quid=20 being discharged from Halon 130= 1 and=20 Halon 1211 has a strong chilling effe= ct on=20 objects and can cause frostbite and b= urns=20 to the skin. The liquid phase vapori= zes=20 rapidly when mixed with air and=20 there- fore limits this hazard= to=20 the immediate vicinity of the=20 nozzle.=20

Scott Krueger=20 AKA Grayhawk
N92EX IO320 Aurora, IL (KARR)

Some Assembly Required=20
Using Common Hand Tools.