Concept Fire Suppression Ltd has been using CO2 for many years as a fire suppression agent and it is very versatile. It can be used on many different applications as well as being used on Total Flood Systems (enclosure) and Local Applications (protecting a piece of equipment in an open area). Unfortunately concentration levels required as a fire suppressant are lethal to humans and can therefore only be used in unoccupied Total Flood enclosures and with care in Local Application systems.
CO2 as a Fire Suppression agent extinguishes a fire by cooling and reducing the oxygen content, thereby removing two elements required by the fire triangle.
CO2 Fire Suppression has been used on print machines, rotating machinery, electrical cabinets, transformers and flow solder machines to name just a few, due to its flexibility of design.
CO2 is stored as a liquid under it’s own vapour pressure and when exposed to air will expand to about 0.52m3 of gas per 1Kg of liquid at 10deg C. It is 1.5 times as dense as air; it is colourless, odourless and electrically nonconductive. As CO2 is heavier than air care must be taken in areas such as pits or floor voids as it will accumulate in these areas.
The standard design concentration is 34% by volume which is then multiplied by a volume factor and then material conversion factor to ensure correct levels of concentration. It can be used on class A fires, wood, paper & fabric class B fires, flammable liquids and class E fires, electrical.
The hold or retention time is 20 minutes twice that of inert gas and clean chemical agents, although this may have to be extended to allow for the burning material to cool.
There are two main types of hardware namely High Pressure and Low Pressure. High Pressure systems normally use a 62L cylinder holding 45Kg of CO2 although smaller cylinders are available. Multiple cylinders use a manifold to connect the cylinders together and discharge through standard Schedule 40 pipework to the nozzle. As CO2 is odourless an odouriser is fitted and where manual lock or valves or Zone Valve system is used burst discs are utilised to protect the pipework against over pressure as Co2 expands exponentially when heated.
Low Pressure systems utilise larger tanks which store enough gas for multiple actuations or multi area systems. These are much less common nowadays but are very useful for protecting larger sites or where continuous protection is required without the need for storing large amount of cylinders within the premises.
Any enclosure that is protected by CO2 Fire Suppression should have interlocks so that anyone entering the room is protected. This ensures that system will be isolated during those times to protect the people entering.