Extinguishing in Brief

In general, fixed systems are designed to extinguish a fire by reducing the oxygen level. Our atmosphere oxygen ambient is 21%. A fire requires a consistent oxygen level of 18% and above. However a person can breathe as low as 12%. So in most circumstances systems are designed to lower the oxygen to approximately 15%. This ensures life can be supported at all times whilst the fire is starved of the required oxygen rate.

The only system that can kill both fire and persons by design is CO2 (Carbon Dioxide). CO2 lowers oxygen to 0%. However CO2 should be, and is normally placed in unmanned areas.

All Fixed systems have the same layout and are produced bespoke to any given area. They consist of high pressurised cylinder/s, a pipe network to distribute the agent evenly, and nozzles to throw the agent in the right direction and at correct speed and consistency.

There are many types of Gases and trade marks available, but they all fall into four categories – Chemical, Inert, Liquid & Water based products.

Chemical types

Suits best; small to medium areas.

These are man made and manufactured specifically for fire fighting use; these are typically HFC227ea, and Novec1230. They are designed for full flood 3 dimensional purposes.

Pressurised via a small addition of nitrogen, to a low pressure of 25 bar, this agent is best situated close to or in the protected enclosure with short lengths of pipe in between the cylinder and nozzles. If the length of pipe is exceeded due to the cylinders being a long distance from the nozzle positions, extra cylinders, larger bore pipe work and a possible manifold arrangement has to be employed. This will result in considerable rise in costs. So best installed very near or in the protected area.

Inert types

Suits best; medium to large areas.

These use gases extracted from our atmosphere, these are typically made of Argon or Nitrogen. These are typically known as IG55, IG541, IG100, and IG01. All inert systems on the market either use one of the mentioned gas type, a blend of, or in the case of IG541 a small amount of CO2 is added. They are designed for full flood 3 dimensional purposes.

Pressured by a high compressed force, these cylinders can be store up to 300bar in order to hold more gas; these systems do not suffer from pipe length restrictions. The cylinder bank can be up to 2km in the most extreme circumstances. However high material requirements in cylinders, means costs are still kept high and in line with chemical types.

Liquid types

Suits best; un-manned areas.

This is another inert gas extracted from our atmosphere known as CO2, but when cooled and pressurised, it becomes a liquid. CO2 can be used for surface, risk specific or full flood 3 dimensional purposes.

Pressured by compressed force, these cylinders can be store up to 45bar to hold more liquid gas and they do not suffer from pipe length restrictions. The cylinder bank can be up to 0.5km in the most extreme circumstances.

Water based types

Suits best; small to medium areas.

Using de-ionised ordinary water propelled by high pressure nitrogen. These are typically known as Water mist systems. They are for risk specific 2 dimensional purposes such as electrical and chemical fires, but turn 3 dimensional when the mist contacts a high heat source (becomes Steam). However at present, there is no third party accreditation or EN standards to work with, and some early systems had hidden issues, so therefore G8 Fire will not promote use of such systems. G8 Fire will be involved once EN standards are in place so as the correct design, definitions and manufacturer accreditations are observed at all times.

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