fire suppression

[John Fitzpatrick]

Some of the large turbine-driven natural gas compressors I worked around in the '70's were protected by nylon tubing pressurized with Halon gas. In the event of a fire, the nylon would melt releasing the halon at the point of combustion. The theory was that this would gain time to mount an appropriate response without cutting off the heat in half of New England.

I've been looking over the available fire suppression options and will probably go with a Halon flood system, but the only two activation methods I've come across have been electrical or mechanical, both of which assume the driver is aware of the fire, conscious, and able to act. I'm wondering if, in addition to cockpit protection, something like the pressurized tubing arraignment deployed in the engine compartment might give a driver time to stop and bail before a situation got unsurvivable, or give a corner worker a few extra minutes if the driver were incapacitated in a wreck. I realize Halon is toxic high concentration, but then, so is flame... Is this being done now or is it one of those elegant solutions to a non-existant problem?

 

[Nick]

John,

It may be different in the US but I believe production of Halon has been banned in the UK since the mid 90's and you can only use recycled supplies.

I work in the Telecomms industry were it was used a lot in the equipment rooms. We were always told if it ever went off to get out quick as it worked by sucking the oxygen out of the air.

 

[EGLITOM]

Dear John

check this out

3M

used in this systems.

Zero 360 Series (FIA)

my understanding is that they are clean and not hazardous.

Thanks
TOM

 

[John Fitzpatrick]

John,
It may be different in the US but I believe production of Halon has been banned in the UK since the mid 90's and you can only use recycled supplies.
I work in the Telecomms industry were it was used a lot in the equipment rooms. We were always told if it ever went off to get out quick as it worked by sucking the oxygen out of the air.

Nick-
After reading your reply I researched the subject a bit more thoroughly last night and this is part of what I found out.
Halon production was restricted by the Vienna Convention for the Protection of the Ozone Layer (the 1985 Montreal Protocol) because of environmental concerns. As a fire suppressant, unlike CO2 and argon which displace breathable air and are potentially deadly if used in a confined space, Halon disrupts the chemistry of combustion¹and is non-toxic enough to be approved by the FAA for use in aircraft cabins³. Here in the States "...there are no federal or state regulations prohibiting the buying, selling or use of Halon extinguishers. Exposure to Halon 1301 in the 5 to 7 percent range produces little, if any, noticeable effect. At levels between 7 and 10 percent, mild central nervous system effects such as dizziness and tingling in the extremities have been reported.²

Halon 1211, CBrClF₂, is a streaming agent used principally in hand-held extinguishers, and Halon 1301, CBrF₃ and Novec 1230, C₆F₁₂O, are total flooding agents. All three discharge as a liquid which immediately flashes to a gas that does not short electrical/electronic equipment and leaves no residue.

All that would seem to make them ideal suppressants to use in a race car's interior, engine compartment, and perhaps around the fuel cells, but apart from Novec 1230 which is FIA approved, I have no knowledge of what other sanctioning bodies might require or permit. I'd still be interested in hearing whether a burn-through type actuation might be worth looking into.

¹NFPA 12A Standard on Halon 1301 Fire Extinguishing Systems, 2004 Edition / Annex D, Hazards to Personnel , section D.2.2
²EFFECT OF CF3H AND CF3Br ON LAMINAR DIFFUSION FLAMES IN NORMAL AND MICROGRAVITY
B.A. VanDerWege,
University of Michigan, Ann Arbor, 1994
³ Federal Aviation Administration
Advisory Circular AC 20-42D, Hand Fire Extinguishers for Use in Aircraft, January 14, 2011