Lawrence Webster Forrest (LWF), Fire Engineering and Fire Risk Management Consultants
Lawrence Webster Forrest (LWF), Fire Engineering and Fire Risk Management Consultants


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Lawrence Webster Forrest
Legion House
Lower Road

Tel: +44 (0)20 8668 8663 Fax: +44 (0)20 8668 8583

Facilities Management & Fire Safety - Gaseous Systems - Part 23

Posted by LWF: 31/08/2017 15:04

In this blog series on fire safety and fire protection methods for people who work in Facilities Management, we are looking at fixed fire-fighting systems and how they are used to protect a building and its occupants in case of fire. 

Although sprinkler systems are very commonly used, they are not the only fixed fire protection system in use in the UK and around the world. In Part 22, we talked about the use of gaseous systems over the years and what gases are in use following the wide-scale banning of halon in 2003.  In Part 23, we’re going to take a look at the clean gaseous agents which have been created since that time, which, unlike halon, don’t have a detrimental effect on the ozone layer.

The new agents which have been developed can be put into two categories –
halocarbons and inert gases. Halocarbon gases are similar in chemical composition to halon, however they are created to cool the flames of the fire rather than interrupting the chemical process of the fire. This means that while it is less harmful to the environment, it is not as efficient as halon 1301, leading to the need to use it in higher concentrations to match effectiveness. 

The agents used in halocarbon gases are hydrofluorocarbons, such as HFC 227ea (CF3CHFCF3, being the most commonly-used), and a fluorinated ketone FK-5-1-12 (CF3CF2C(O)CF(CF3)2, which is known commercially as Novec 1230. Other halocarbons are in use, but are very rarely seen in the UK.

Inert gas systems work entirely differently to halocarbon gas systems. The role of the inert gas is to reduce available the oxygen concentration in the affected area to a point where the fire simply cannot be sustained. 

The modern inert gas systems are safer than CO2 systems in areas where a CO2 system cannot be used due to the dangers for living beings, although they work largely on the same principle. The amount of oxygen left in the applicable area after the use of one of the newer inert gases is capable of sustaining life.

There are four main inert gas agents in use in an inert gaseous system. These are:

IG-541 (52 percent nitrogen, 40 percent argon and 8 percent CO2)
IG-55 (50 percent argon and 50 percent nitrogen)
IG-01 (100 percent argon)
IG-100 (100 percent nitrogen)

The chemical composition is one way in which the inert gases and the halocarbons differ, but there are other factors which will affect the choice of which type of system is most appropriate for a given situation or building.  

In Part 24 of this series, we will look at those influencing factors. In the meantime, if you have any queries about your own facilities or wish to discuss this blog series, please contact Peter Gyere in the first instance on 0208 668 8663.

Lawrence Webster Forrest is a fire engineering consultancy based in Surrey with over 25 years' experience, which provides a wide range of consultancy services to professionals involved in the design, development and construction and operation of buildings.

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