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What is a Halon system?

As I keep reading stuff such as "the hacker test", I keep hearing about Halon systems.

What is a Halon system?

How is it related to supercomputers?

Thanks!

Bob
Monday, November 24, 2003

A simple google search on Halon returns tons of links...


Basically, Halon is a CFC gas that was used in fire suppression systems - especially where expensive electronics were used since it doesn't damage the electronics.

It isn't being deployed anymore since it is a CFC (like Freon) and can damage the ozone layer. Existing installations can still use Halon, until it is used - it then needs to be replaced.

The only place that uses new Halon systems are military aircraft. The low weight combined with the excellent fire-extinguishing properties makes it almost irreplaceable there.

RocketJeff
Monday, November 24, 2003

Isn't Halon an inert gas not a CFC?


Monday, November 24, 2003

Nope.
The first link google popped up:

http://www.h3r.com/halon/

They have data sheets for various forms of Halon. All are CFCs and all the MSDS sheets include the ozone layer warning.

Michael Kohne
Monday, November 24, 2003

Of course you are right.  My chemistry teacher taught Poetry as his main discipline.


Monday, November 24, 2003

I'm not sure that Halon is a 'true' CFC, since a Chlorofluorocarbon (CFC) is a compound consisting of chlorine, fluorine, and carbon. Halon is a compound consisting of bromine, fluorine, and carbon. Bromine is, however, many times more effective at destroying ozone than chlorine so I doubt if the distinction of whether it is a 'true' CFC is important.

It is definately not an inert gas.

RocketJeff
Monday, November 24, 2003

Blank, halon's name does sound a bit similar to the names of the various noble gases (helium, neon, argon, krypton, xenon, radon), but it's neither an element nor inert.

John C.
Monday, November 24, 2003

"Inert gas" and "CFC" are not mutually exclusive. Freon is both a CFC and an inert gas, and I thought other CFC's are inert too but I'm not sure about that. It's one of the reasons of the widespread use of CFC's: being inert implies being non-toxic, non-corrosive etc.

Roel Schroeven
Monday, November 24, 2003

More tips can be found here:

How To Ask Questions The Smart Way
http://www.catb.org/~esr/faqs/smart-questions.html

StickyWicket
Monday, November 24, 2003

Freon is *not* and inert gas. It is a compound. The inert gases are all atomic (Argon, Krypton, Neon,...). Freon is a trade name of a CFC compound made to sound like it's a noble gas.

pdq
Monday, November 24, 2003

I knew a guy (mainframe technician) who was in a large computer room when the Halon system accidentally went off.  He had half his body under the raised floor, snaking a cable or something.  When he heard the alarm, he climbed out, and sprinted to the door.  By the time he got there, it was time for another breath.  Fortunately, someone saw him and opened the door for him, saving him a few seconds, and probably from passing out...

Grumpy Old-Timer
Monday, November 24, 2003

Inert is not a synonym for noble, and neither does compound exclude inert.

From "Chemistry" by Mortimer, 6th edition:

'Mixed chlorine-fluorine compounds of carbon (in particular CCl2F2) are called the "freons." They are very stable, odorless, nontoxic gases that are used primarly is refrigerants.'

Maybe 'very stable' is not the same as 'inert', but it certainly comes close.

Roel Schroeven
Monday, November 24, 2003

And from Wikipedia, on the page about inert gas:

"An inert gas is a non-reactive gas and is usually a member of the noble gas family. Examples include: helium, neon, argon, xenon, krypton, and radon."

"Usually is not the same as "always".

Roel Schroeven
Monday, November 24, 2003

30 years ago, there was no way to react the elements in the right hand column of the periodic table. They were called inert gases. Then someone found a way to react them under extreme conditions. So, they changed the name from inert gases to noble gases.

see http://www.carondelet.pvt.k12.ca.us/Family/Science/Noble%20Gasses/Noble%20gases.htm

for details.

pdq
Monday, November 24, 2003

>>> I knew a guy (mainframe technician) who was in a large computer room when the Halon system accidentally went off.  ...<

Was this really a Halon system?  Halon is not only harmless to the electronic equipment, it is harmless to the people in the room.  Or at least it is supposed to be.  He should have been able to survive in the room with no problem.

I have seen rooms with fire suppression systems that release carbon dioxide in to the room.  This kind of system would kill the fire and the people in the room, too. 

A disadvantage of Halon is that it is really expensive.

mackinac
Monday, November 24, 2003

From:

http://www.tpub.com/content/advancement/14146/css/14146_124.htm

The  short  discharge  time  of  Halon  1301  (10 seconds maximum) keeps the thermal decomposi- tion  products  well  below  lethal  concentrations. The real hazard lies not in the by-products of the halon, but rather in the products of combustion from  the  fire.  Products  such  as  CO,  combined with the oxygen depletion, heat, and smoke, pose a greater hazard to personnel. Personnel should not remain in a space where Halon 1301 has been released  to  extinguish  a  fire  unless  an  oxygen breathing apparatus (OBA) is worn. If Halon 1301 should  inadvertently  be  released  into  a  space where no fire exists, personnel can be exposed to 5-to-7  percent  concentrations  of  Halon  1301  for up  to  10  minutes  (depending  upon  the  individual) without  danger  to  their  health.  Halon  1301  can be  considered  a  nontoxic  and  nonsuffocating extinguishing agent in the normal 5-to-7-percent concentrations;    however,  spaces  should  be evacuated  on  halon  system  discharge.

DJ
Monday, November 24, 2003

So, how does Halon *work*?

Bob
Tuesday, November 25, 2003

So, how does Google *work*?

Robert Jacobson
Tuesday, November 25, 2003

Dear Sir,

Before posting my question to this forum, I have toroughly searched using Google, and I could NOT find the following information:

- what is a Halon system

- how does it work

The only thing I could find was sites of companies that offer Halon replacements, etc - nothing about what a Halon system IS and how it WORKS.

Bob
Tuesday, November 25, 2003

... such as this page:

http://www.fm200.biz/halon.htm

Now, how does this page answer the questions above?

It seems that Halon is something that is very old, and that's why there are no web pages about it.

Bob
Tuesday, November 25, 2003

Interesting, that page you cite has _exactly_ the information you want, if you scroll down about a page or two...

"What is Halon 1301
Chemically - BTM (bromotrifluoromethane) 1301: An excellent fire extinguishing agent (gas) currently installed in thousands of locations throughout the world protecting sensitive electronic equipment, typically found in computer rooms, telecommunications centres, data processing environments, aviation and may other places."

That's just the first q/a on their halon faq - wich is entirely on the same page.

RocketJeff
Tuesday, November 25, 2003

Also, if you search google for specifics, you get better searches.

Searching on "haylon how it works' give that question/answer (in exactly that form) as a link on the first page returned by google.

RocketJeff
Tuesday, November 25, 2003

If you still don't know how it works, surf to www.wikipedia.org and search for halon.

Roel Schroeven
Tuesday, November 25, 2003

The commenter who said that halon is not a CFC is correct - it's a brominated compound, not a chlorofluorocarbon. And it's true that bromine is much more effective, molecule for molecule, than chlorine in destroying ozone.

Halons are very stable compounds at ground level, but once they get into the lower stratosphere and are bombarded by intense solar radiation, they eventually break up...that's how the bromine gets involved in ozone depletion.

Some people used to question how compounds like halons and CFCs could ever make it up to the stratosphere, since they're heavier than air, but remember that even dust is heavier than air and plenty of that gets up to the stratosphere as well. Winds and updrafts carry these compounds into the atmosphere, where they can last for years before breaking up. They only cause damage to the ozone layer after they break up.

Some of the CFCs from the hairspray that Elvis Presley used in the 1960s and 1970s are probably still floating around in the stratosphere. The long life of these compounds in the atmosphere is the reason why, even though most production and use of CFCs and halons was banned in industrialized countries by 1996, the seasonal ozone hole over Antarctica is not expected to go away until the middle of this century.

Brad
Tuesday, November 25, 2003

(BOFH Mode on)

I thought it was gassing nosey users.

(BOFH mode off)

A cynic writes
Tuesday, November 25, 2003

Bob's questions illustrate an interesting characteristic of the web.  For all the information that is available, sometimes you can ask a simple question and not find the answer in the deluge of pages that Google can find for you.

I did take a look at http://www.fm200.biz/halon.htm which Bob mentioned and could not find the answer to his question there either, although other posters claim to have found the answers.  The wikipedia wasn't of much help either.

It also illustrates a basic characteristic of questions: some are obvious and others are simple but not obvious.  This one is simple, but definitely not obvious.

By now you probably know most of what there is to know, but just to be sure there are not too many missing details, I'll make my own attempt at explaining what a Halon(tm) system is for someone who has never heard of it:

- In the context of a computer room, where a large mainframe, possibly a "supercomputer", might be installed, a Halon(tm) system refers to a fire extinguishing system.

- The system consists of a canister of the Halon gas, a system of pipes and nozzles for dispensing the gas, an electrically operated release valve, and a fire detection system (smoke and heat detectors).

- When the fire detection system senses a fire in progress, the entire contents of the Halon cannister are dumped into the atmosphere in the room being protected.

- Fire requires fuel, oxygen, and heat.  Fire extinguishers normally eliminate one of the three (water eliminates heat, CO2 displaces oxygen).  Halon works differently.  It interferes with the oxidation reaction between the fuel and oxygen.  Thus, it can work a fairly low concentrations in the atmosphere.

- Advantages of Halon for fire extinguishment are: doesn't damage equipment as might occur with sprinklers, and doesn't damage people as would occur with CO2.  Although, as others have noted, if there really is a fire you would want to leave the area quickly anyway.

- Disadvantage: expensive.  Also, ozone depleting, but there may be alternatives that don't have that problem, but may be even more expensive.

mackinac
Tuesday, November 25, 2003

--"water eliminates heat"----

I thought water extinguished fires by smothering them - that is to say placing a layer between air and the oxygen needed.

Stephen Jones
Thursday, November 27, 2003

Water also removes the heat, which is why you'll see firefighters dousing adjacent structures (if the buildings are close enough).  This is also why they will continue to douse an otherwise ‘out’ fire with water – I’ve seen fires that were out flare back up because the wood was still very, very hot.

The material will light if it reaches a hot enough temperature.

MR
Sunday, November 30, 2003

I just bought a fire extinguisher for my boss' car at

http://www.h3r.com/products/home_vehicle.htm

informative site

CD
Monday, August 16, 2004

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