Fixed Fire Fighting - Gas
Halon 1301 Bromotrichlhoromethane CF3Br
A colorless odourless gas. As a gas it is non-corrosive, when it is dissolved in water it is highly corrosive .Nitrogen for super-pressurisation is added due to the low pressure energy of halon, typically to 42bar at 20oC
by a little understood process it disrupts the chain of reaction that is combustion thus extinguishing fires.
When comparing toxicity to extinguishing concentration halon is the safest agent. Concentrations upt to 7% can be breathed for 5 minutes without effect, at 10% this is reduced to 1 minute.
At a temperature above 510oC halon will decompose. Two of the most important products are Hydrogen Bromide (HBr) and Hydrogen Fluoride (HF). In small concentrations these gases are an irritant which will forewarn personnel of increasing concentrations.
It is considered that these gases pose a much lesser threat than the other products of fire- poisonous smoke, carbon monoxide etc.
A concentration of 4.25 to 5% by volume is required
Following the Montreal protocol the usage of Halons was agreed to be phased out by the year 2000 and halved by the year 1995.
In response to this, IMO has planned the following;
With regard to the second requirement, guidelines state that Halon should only be used as a fire fighting medium in a space where there is no other suitable means of extinguishing the fire to protect personnel and property. This guideline is only valid until January 2000. Companies are required to replace there fire fighting Halon with a suitable alternative, it is envisaged that companies will have difficulty in restocking Halon systems as the production of these gasses is phased out by industry. It is a requirement that they have a suitable alternative method fitted should the system be utilised and so it is in the operators best interest to replace the system at their convenience rather than as necessary. Halon systems are still in use as of August 2000