Re:Halon and Flames

[Regan Dale Copple <copple@xxxxxxxxxxxxxxxxxxxxxx>]

Alfisti,
	My apologies to all, I let my temper get the best of me.
	But some people sent in some interesting posts, both concurring
and disagreeing with my post.

On Date: Wed, 25 Nov 1998, Robert A Brady at Robert_A_Brady@domain.elided )
wrote:
 
> Halon extinguishes flames by scavanging the Hydrogen radicals.  For 
> combustion to continue (propagate), hydrogen radicals are required to split 
> the Oxygen molecules forming an Oxygen radical and a hydroxy radical.  

> Halogens such as Bromine and Florine are more reactive with the hydrogen 
> radicals than the O2 is, so they wind up scavanging the hydrogen and thus 
> combustion can't propagate.

> CO2 and dry chemical extinguishers, on the other hand, work by displacing the 
> oxygen from the fuel.  Water extinguishers work primarilly by cooling the 
> reactants which slows the propagation reactions down to the point where they 
> terminate before they can continue.  Metal fires don't depend on hydrogen 
> radicals to propagate, and therefore Halon is worthless on them.  I'm not 
> sure how you put out a metal fire (i.e. what's in the metal fire 
> extinguishers), but I'd suspect they are some inert ingredient that displaces 
> the oxygen from the fuel.  

	The way you put out a metal fire such as a magnesium is to use
what they call PKP or purple K powder, what essentially is powdered
potassium mixed with something else, I'm not exactly sure.

On  Wed, 25 Nov 1998, Rich Wagner at <drsavage@domain.elided> wrote:

> >	Now, for an interesting aside, how does Halon extinguish a fire if 
> >it neither cools the flame, displaces the oxygen, or removes the 
> >fuel?  The Navy, my esteemed employer, had to re-invent fire to solve 
> >this little delima.
> 
> Halon is a fairly massive compound.  According to my colleagues who develop
> Naval aircraft fire fighting techniques, it does, in fact, displace the
> atmosphere.  It also requires a very large oxygen ratio for ignition, and
> so it starves the fire by providing an impossibly rich mixture.
> 
> 
> Rich
> Manitou Springs, CO
> '82 GTV6 Balocco

	Kudos to Rich, that is also always what I've heard, the
electrochemical interruption of the combustion process may be a
beneficial secondary process, or maybe they thought we were all too stupid
to understand the process, but usually they explained things quite
completely to us in firefighting school.
 
On  Wed, 25 Nov 1998, Bob Rand at <r-mrand@domain.elided> wrote:
> Subject: re: The flaming process and halons
> 
> When the fuel and air are at the correct mixture and an ignition source is
> introduced, fire will occur.  The flame is a combination of the
> decomposition of the fuel and the oxidizing agent (air).  This is called the
> uninhibited chemical chain reaction.  As the fuel burns, it releases heat,
> causing more vapors to burn, and they ignite.  Also as this chemical chain
> reaction occurs, it releases free chemical radicals in the flame area of the
> fire.  Halon which is no longer produced such as carbon tetrachloride,
> chlorotrifluoromethane, and chlorofluorodibromomethane) when introduced to
> the flame, break down into free radicals also.  These free radicals combine
> with the ofther free radical released from the burning process and make
> stable molecules.  Therefore, the flame goes out.  Be careful though, the
> liquid may still be producing vapor, oxygen is present, and an ignition
> source may be present which will start the process all over again.
> Hope this was not too confusing.

> Bob Rand
> Fire Instructor IV, Massachusetts Firefighting Academy
> Hazardous Materials Technician, Massachusetts Department of Fire Services
> 1987 Alfa Spider Quadrifoglio

	I never heard of using carbon tet as Halon, it's more common use
is as a dry cleaning fluid.  But if the halon breaks down into free
radicals then I definitely wouldn't want to be in the room, free chlorine
can burn the shit out of your eyes, nose, and lungs.  Not to mention free
fluorine which is even more electronegative than chlorine.  If the free
radicals are only the halogenated hydrocarbons then that's somewhat better
but not much as far as toxicity is concerned.

Finally,
On Wed, 25 Nov 98, Jeffrey Weiss at <weissj@domain.elided> wrote:
> Subject: Re: Tour de Turkey 98
> 
> > This Saturday, I will be taking the GTV6 ITS car to participate in the
> > SCCA SowDiv six hour "Tour de Turkey" club race at Texas World Speedway.
> > This will be a chance to see an Alfa in the heat of battle at TWS.
> 
> My Alfa will be in the heat of battle at the East Coast version.  Our Tour de
> Turkey consists of six hours on the Long Island Expressway.  Total distance
> covered will be about 40 miles.  Anyone wanna come out and crew for me?

	Jeff, I once did the SoCal Tour de Turkey, three hours to get from
Long Beach to the north end of San Fernando Valley, I about peed my pants
trying to wait until the traffic cleared up before I pulled off the 405.

	Cheers to all, Have a Happy Thanksgiving!

						Typing with five fingers,
						Regan Copple
						79 Spider-black
				(coming soon)-->72 Montreal-silver
						73 Montreal-black

"It is amazing how complete is the delusion that beauty is goodness."
					-Lev Nikolayevich Tolstoy

"Genius is nothing but a better aptitude for patience."
					-Benjamin Franklin

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