Remaining uses of Halon fire extinguishing equipment on railways

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thenorthern

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So I was looking at fire extinguishers for a friend of mine and I noticed that there used to be a gas used until the 1990s called Halon which apparently is great at fighting fires but it removes the ozone layer so they were banned except for certain critical purposes.

Apparently the main exemption is for aircraft but also the Channel Tunnel has an exemption because of the critical nature of safety in the tunnel.

I was wondering though is the Channel Tunnel the only one with the halon ban exemption or is Halon also used to fight fires in other places such as the London Underground or other places.
 
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billh

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So, there is a fire, people and property are in danger, the fire needs to be put out ASAP.(It's an emergency!) Halon was the best fire extinguisher by far, but it allegedly damages the ozone layer at some point after the emergency.
If some other means of putting out the fire was used, which then took longer to achieve, was the Ozone or any other part of the atmosphere damaged by the products of combustion emitted during the extended fire? Probably. The (non BR) computer machine room ( mainframe , remember them?) where I worked had fixed halon systems that had thankfully never been deployed. It was all dismantled and a different less effective system put in at huge expense , a pointless exercise in my view.
 

John Webb

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I agree with billh's comments. At the time of the Halon ban, I was on the scientific staff working for the then government-owned Fire Research Station at Borehamwood. We were never approached to carry out an assessment of which did more damage to the environment - products of combustion from uncontrolled fires or the halons used to put them out quickly - before the decision was taken by the politicians.

The police and the armed forces are still allowed to use halons for certain risks, as well as aircraft.
 

EveningStar

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Halon emissions into the atmosphere decreased rapidly following 2000, although research suggests halons continue to account for ~30% of ozone depletion (see Atmospheric histories and global emissions of halons H-1211 (CBrClF2), H-1301 (CBrF3), and H-2402 (CBrF2CBrF2), http://onlinelibrary.wiley.com/doi/10.1002/2015JD024488/full). Continued restrictions on halons, even if infrequently used, seem indicated, although more research along the lines suggested by John Webb would be interesting. Recent interesting paper in the journal Fire Investigation on alternative fire suppression systems in aircraft (Fire suppression systems in aircraft: Their past, present & future, http://researchopen.lsbu.ac.uk/535/).
 

Randomer

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Although I agree with the above posters about the efficiency of Halon vs the combustion products produced wasn't the ban more about accidental releases when systems were tested, damaged or decommissioned (or deliberate in some cases as doing it right cost more money). A fire dousing system is incredibly unlikely to be used against the likelihood of leaks or other damage in a pressurized system.
 

thenorthern

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I think its more that the manufacture of Halon would let off ozone depleting things regardless of if it was used to fight a fire at a later date or not.

Halon though is like Leaded Petrol, Asbestos, open air nuclear testing, CFC sprays, leaded paint, indoor smoking, hyperactive food colours, wooded escalators, hopper toilers and town gas where is something that was in use regularly that was really incredibly dangerous.
 

route:oxford

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The (non BR) computer machine room ( mainframe , remember them?) where I worked had fixed halon systems that had thankfully never been deployed.

Ours was. A colleague was told he had to work his notice and in a pique of temper, went into the server room, hit the "kill" switch and activated the Halon extinguishers.

From that moment onwards, nobody worked their notice and were immediately escorted from the company premises when they handed in their notice.
 

bus man

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Not sure if it’s the same gas but the police had an exemption on one of the banned fire extinguishers.

They could use them if some one set fire to them self’s, if police were dealing with protest marches the extinguishers were carried otherwise they were banned the gas in them was very quick acting. Not sure what the gas was
 

John Webb

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Not sure if it’s the same gas but the police had an exemption on one of the banned fire extinguishers.

They could use them if some one set fire to them self’s, if police were dealing with protest marches the extinguishers were carried otherwise they were banned the gas in them was very quick acting. Not sure what the gas was
It is "BCF" - Bromo-Chloro-Diflouromethane (which is why the trade and others call it BCF!) also known as Halon 1211.
 

Elecman

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The old Foundries at BREL Horwich must have accounted for a fair proportion of the Ozone hol3 then as we were using about 30+ BCF extinguishers a week after the disasterous fire in the late 70s. :lol:
 

tellytype

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Still use & keep a large stock of Halons/BCFs, including one in the car. Still the best extinguishant there was/is.

Sorry but if my life & safety depends on it, I'm using the Halon & to hell with the greenies!
 

Crossover

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Going back quite some time, I was of the belief that Halon was a bad idea as it can be dangerous to humans (rather than just unpleasant as some gases are) so wasn't used

A fire suppression system I have some involvement with (not rail related) currently uses HFC something or other - the bottle (around 40kg we think) needs replacing but is in the loft and getting it down won't be easy - I did suggest 'using' it before removing a more lightweight bottle, but was advised that this is o-zone depleting too.
Another thing that was pointed out to me too, was that they are often suppression systems, not extinguishants such that if the fire isn't out completely once the bottles run out, it'll re-ignite again
 

aar0

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Still use & keep a large stock of Halons/BCFs, including one in the car. Still the best extinguishant there was/is.

Sorry but if my life & safety depends on it, I'm using the Halon & to hell with the greenies!

Yeah, screw the greenies... and the planet.

Am I correct in thinking halon grabs onto all the oxygen in a room? And so is "non-life supportive" after use?
 

cactustwirly

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Yeah, screw the greenies... and the planet.

Am I correct in thinking halon grabs onto all the oxygen in a room? And so is "non-life supportive" after use?

I don't think so, I believe it reacts similarly to a CFC so it catalyses the breakdown of ozone to diatomic Oxygen.
I think 1 molecule of Halon can breakdown hundreds of Ozone molecules
You won't be staying "to hell with the greenies" when the Ozone layer is destroyed, and you've got skin cancer because of the harmful UV radiation.
 

edwin_m

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As I understand it these fire suppression systems work at least partly by displacing the oxygen in the room with an inert gas so there is nothing to support combustion. So whatever gas is used there would be a danger of asphyxiation to anyone in the room at the time. Clearly there must be more to it than that, otherwise they would use something simple like nitrogen rather than a more damaging and no doubt more costly chemical such as Halon.
 

AndrewE

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As I understand it these fire suppression systems work at least partly by displacing the oxygen in the room with an inert gas so there is nothing to support combustion. So whatever gas is used there would be a danger of asphyxiation to anyone in the room at the time. Clearly there must be more to it than that, otherwise they would use something simple like nitrogen rather than a more damaging and no doubt more costly chemical such as Halon.
Halons are chemical agents that break up in the fire and then react with the fuel or oxygen molecules, stopping the chain reaction of "fuel plus oxygen gives heat plus CO2" Other extinguishants either take the heat away (water) or the oxygen (CO2) and stop the fire in that way. I certainly wouldn't want to inhale "activated" Halon as I'm sure it would latch on to the fuel in my body in the same way. Cold halons are relatively inert so will just be asphyxiants. In the upper atmosphere the UV radiation in sunlight breaks them up like the heat of the fire does, allowing the reactive bits to react with the ozone.
 

billh

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Anyone remember "Pyrene" extinguishers, often fitted to rail and road vehicles and also found in industrial premises*?
These were filled with carbon tetrachloride in a small brass hand pump device , hung on wall brackets. CTC was great at putting fires out but the combination of that chemical and high heat caused phosgene gas to be emitted which is very dangerous to life ,so much so that it was used in wartime against the enemy. Rightfully banned as it was far more toxic than Halon ever was.

* Many years ago I worked in a large electronics factory, actually a converted cotton mill. There were dozens of Pyrene extinguishers around the place. The security guards used to regularly polish the units with Brasso and they always looked very smart (the extinguishers that is!) . Trouble was , the instruction labels for use in event of fire became illegible due to the frequent polishing.......
 

fireftrm

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Halon extinguishant was stopped worldwide, not just the UK, through a treaty. Anyone with a halon extinguisher should serioulsy consider the danger they are placing themselves in, not only are the by-products of its use on a fire potentially hamrful but it can be an asphixiant in a closed space (like a car). Furthermore the extinguisher will be a pressurised gas cylinder and should be subject to a hydrostatic test at 10 year intervals. In other words it may no longer be safe to carry as none have been manufactured for over 20 years......
 

MarkyT

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I recall in my early railway career that some signalling relay rooms had extinguisher systems that would flood the space with a fire suppressant gas if an alarm triggered. There were isolation valves near the entrance doors to prevent discharge if technicians were working in the room. It's possible some of these were halon originally. Fire in a large relay interlocking would be a very serious issue. A major unchecked conflagration could quickly cause sufficient damage to put the full facilities of the railway in the affected area out of action for months whilst hundreds of new relays and thousands of new wires were installed and tested.
 

John Webb

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Anyone remember "Pyrene" extinguishers, often fitted to rail and road vehicles and also found in industrial premises*?
These were filled with carbon tetrachloride in a small brass hand pump device , hung on wall brackets. CTC was great at putting fires out but the combination of that chemical and high heat caused phosgene gas to be emitted which is very dangerous to life ,so much so that it was used in wartime against the enemy. Rightfully banned as it was far more toxic than Halon ever was.

* Many years ago I worked in a large electronics factory, actually a converted cotton mill. There were dozens of Pyrene extinguishers around the place. The security guards used to regularly polish the units with Brasso and they always looked very smart (the extinguishers that is!) . Trouble was , the instruction labels for use in event of fire became illegible due to the frequent polishing.......
Indeed I recall the pump-type extinguishers - another problem they suffered from was misuse to get the Carbon Tetrachloride out to remove grease stains on clothing. Later on pressurised versions were introduced, particularly by Nuswift. I was in a large antique centre in North Yorkshire (the type where numerous dealers have displays) while on holiday in September. There were several of the hand-pump type about, all empty, but there was one nice looking pressurised unit from circa 1970 on display - still fully charged! I quickly drew the attention of the owners to the hazard and it was removed from display.
 
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