A Gas Suppression system is a waterless fire suppressant that functions by releasing a gas, or mixture of gases, into the air with the aim of extinguishing and/or preventing the fire spread within a building.
To understand how fire suppression systems achieve this we should first review the principal aspects of fire chemistry. Four components; fuel, oxygen, heat, and the combustion chain reaction are often referred to as the “fire tetrahedron”.
All four of these factors are required in the correct combination for a fire to ignite and sustain burning. The fire tetrahedron shows that a fire can be extinguished by eliminating one or more of the links between these components or by changing the balance between them;
Gas Suppression Systems are sometimes manually activated; however, most are automatic. An automatic system functions through the conjunction of three key elements; a smoke detector, notification device and control panels.
The smoke detectors are the first line of defence and will alert the control panel if smoke is detected within the vicinity. The control panel will then inform the notification device and the piping to begin releasing the gas into the required location. Occupants of the area will be notified by the notification system and made aware that the fire suppressing agent will soon be released.
The type of gas suppression system used is dependent on a variety of factors such as; storage space for cylinders, installation of pipework, environmental impact, cost etc. Always consult a professional when deciding upon which gas is right for you.
However, here are the three most commonly used gas agents for comparison.
| Novec 1230 | Inert Gas | FM-200 | |
| Type of Compound | A fluorinated ketone contained carbon, fluorine and oxygen. | A mixture of the inert gases: argon, nitrogen, carbon dioxide (CO2). | A hydrofluorocarbon (HFC) compound containing hydrogen, fluorine and carbon. |
| Storage | Stored as a liquid | Stored as a gas | Stored as a liquified compressed gas. |
| Discharge Time | 10 seconds | 60 seconds | 10 seconds |
| Clean Up | None | None | None |
Gas suppression is ideally suited in an area where other forms of firefighting may cause water damage to electrical goods.
For example, a server room where data is stored would benefit from a gas suppression system to protect as much of the data as is possible in the event of a fire.
Furthermore, electrical rooms occupied by employees cannot be fought with traditional firefighting methods as the combination of electricals and water would pose a risk to life.
Conducting a Fire Risk Assessment will reveal if a Gas Suppression System is necessary for your premises, always refer to the RRO 2005 when conducting an FRA.
All gas suppression systems should be tested in accordance with BS 5430-1:1990 where high-pressure cylinders are utilised.
The system should be designed in accordance to the standards BS EN 15004-1 which cover the design, installation and maintenance of the system and guidance on room integrity testing that ensures the areas protected by these systems are capable of retaining the gas on discharge for ten minutes (twenty if the agent involves carbon dioxide).
Testing by BRE, FSSA and others has determined that all suppression systems create over pressurisation upon system discharge. Chemical gases (i.e. FM-200, NOVEC 1230 etc.) create under and over pressurisation upon system discharge. To protect against possible structural damage, it is recommended to install a pressure relief vent that discharges to fresh air.
In protected enclosures means for prompt natural or forced-draft ventilation of areas after any system discharge should be provided, to safely remove fire by-products and extinguishant (as per EN 15004-1 and ISO 14520-1). Forced draft ventilation will often be necessary. Care should be taken to completely dissipate hazardous atmospheres and not just move them to other locations. It should be noted that most extinguishing agents are heavier than air.
