The LWF Blog

Fire Safety for Facilities Management Personnel – Gaseous System Agents – Part 250

April 29, 2024 10:28 am

Lawrence Webster Forrest (LWF) is a specialist fire engineering and fire risk management consultancy whose aim is to give information on best practice in fire safety for facilities management personnel through this blog series. In part 249, LWF began to talk about the specific agents used in gaseous fire suppression systems. In part 250, we continue discussing gaseous suppression and total flooding systems.

The decommissioning of halon installations in 2003 meant that the only readily-available form of gaseous extinguishing system was a CO₂ system, which is highly effective at extinguishing fire, just as halon was. However, in terms of safety, the fact that concentrated use of CO₂ is toxic to humans and animals meant that many users were not prepared to use a CO₂ system or that it would be extremely impractical in areas that would be typically occupied.

The Health and Safety Executive would not oppose the installation of a CO₂ system, provided it was installed in accordance with appropriate safety features. Building occupants can be affected by leakage of the gas into other areas, or the collection of the gas in low areas such as lift pits, therefore great caution must be taken to ensure all areas of the building are clear of CO₂ before it is re-occupied.

Fortunately, alternatives to halon 1301 and CO₂ were developed in the intervening years for use in fixed extinguishing systems for total flooding applications. The two predominant categories of agents are halocarbons and inert gases. These are clean inert gases that are non-toxic to humans and animal life, just as halon was, but are also non-detrimental to the ozone.

Halocarbon agents are chemically similar to halon, although they rely more on cooling the flames than changing the chemical process taking place in the flames. Halon was highly efficient and therefore was able to be used in design concentrations as low as 5 per cent volume/volume. None of the newer halocarbon agents are as efficient in terms of extinguishing capability, and so more agent (and therefore storage containers) is required. The agents include hyrdurofluorocarbons, such as HFC 227 ea (CF3CHFCF3, probably the most commonly used halocarbon), and a fluorinated ketone FK-5-1-12 (CF3CF2C(O)CF(CF3)2, known commercially as Novec 1230). A number of other halocarbons can be used, but their use in the UK is uncommon.

In part 251 of this series, LWF will continue to discuss the halocarbon and inert gases used in total flooding applications. In the meantime, if you have any queries about your own facilities or wish to discuss this blog series, please contact LWF on freephone 0800 410 1130.

Lawrence Webster Forrest is a fire engineering consultancy based in Surrey with over 35 years’ experience, which provides a wide range of consultancy services to professionals involved in the design, development and construction and operation of buildings.

 

While care has been taken to ensure that information contained in LWF’s publications is true and correct at the time of publication, changes in circumstances after the time of publication may impact on the accuracy of this information.