Gaseous Fire Suppression Systems
Gas or Gaseous fire suppression systems are typically used in areas where water damage needs to be avoided. Areas such as computer rooms and archive storage areas are two of the many areas that gas systems are designed to protect. Firecrest Services Ltd offers a full range of systems including inert and chemical gases. The choice of gas is dependent on the areas of use and the level of risk along with the safety of staff that might be in the area at the time of the fire.
Inert Gas Agents
These agents control the fire by causing the oxygen content within the protected enclosure to be reduced to a level that will not support combustion Inert gas agents are electrically non-conductive and clean when used. An example is nitrogen which can be used alone or combined with argon.
Inert gas agents are used in concentrations of 40-55 % by volume. When discharged the oxygen concentration is reduced to between 10 -14%. Oxygen concentrations below 12-14% will not support flaming combustion.
As they use natural gasses inert gas agents have a zero ozone depleting and global warming potential.
Gas mixtures are blended to have a density similar to air, so that in the event of a compartment leak they retain their concentration within the risk area.
Inert gas agents are not subject to thermal decomposition and therefore do not produce any hazardous by products.
A disadvantage of using inert gas agents is that they are stored in high pressure cylinders which are relatively heavy and large.
Examples of inert gas agents are inergen and aragonite.
Typical applications for inert gas systems are:
- Telecommunication facilities
- Computer rooms
- Control rooms
- Transformer and switchgear rooms
- Flammable liquid hazards
- Shipboard machinery spaces
- Record Storage
The systems are designed to operate through double knock point detection and / or the use of VESDA aspirating systems to provide very early smoke detection. Gaseous systems are designed to flood the area with the gas to extinguish the fire.
Firecrest Services Ltd services include integrity testing of the protected areas, the provision of pressure relief dampers and automatic plant shutdown relays.
Chemical Gas Systems (Halo Carbon Gas Systems)
Most chemical agents extinguish a fire through a combination of heat absorption and chemical interference with the combustion chain. Halo carbon agents are stored in liquid form at a lower pressure than inert gasses, and as such take up less volume as their inert gas counterparts. The cylinders are charged with a nitrogen propellant in that, when the gas is released, the nitrogen pushes the liquid extinguishing agent along the pipe work and out through the nozzles. As the chemical is stored at a low pressure, the storage cylinders or vessels may need to be located closer to the protected areas than an equivalent inert gas system.
Examples of Halo Carbon agents are FM-200/FE-227, Novec 1230,FE-25 and FE-13
Typical applications
- Telecommunication facilities
- Computer rooms
- Control rooms
- Aero engine compartments
- Transformer and switchgear rooms
- Flammable liquid hazards
- Shipboard machinery spaces
Carbon Di-oxide
Carbon dioxide protection systems require particular measures to be applied to their use and management as it is both toxic and asphyxiant at the concentration necessary to extinguish fire. When the protected area is occupied the carbon dioxide system must not be on automatic control. The addition of odorises to the system would assist in detecting a discharge as the gas itself is colorless and odourless.
Carbon dioxide is a clean agent with good penetrative qualities, and as such is suitable for use on live electrical equipment. However, as large storage quantities are necessary due to the high storage pressure and concentrations need to be effective, space and weight become important issues that need to be carefully considered. Typical application for carbon dioxide systems are:
- Telecommunication facilities
- Transformer and switchgear rooms
- Record storage
- Flammable liquid hazards
- Shipboard machinery spaces
