The LWF Blog

Facilities Management & Fire Safety – Gaseous Systems – Part 26

September 21, 2017 9:10 am

In LWF’s blog series for those who work in Facilities Management or who have a responsibility for fire safety as a part of their job, we have been looking recently at the use of gaseous systems as a method of fire protection. Gaseous systems are most commonly used in circumstances where sprinkler systems are not appropriate.


In part 25 we talked about the use of fusible links which melt to actuate the release control of the gaseous extinguishing system, known as a mechanically actuated installation. In part 26, we’ll discuss electrically actuated systems and wet chemical systems.


In the case of an electrically actuated system, there will be manual controls and the discharge control most commonly consists of a two-step device, such as ‘lift flap and break glass’ to avoid accidental discharge. A manual release should be situated outside the exit of the area in question so that the occupant instigating the activation of the system is no longer inside the area and in danger from the fire or from side-effects from the gas released.


An electrically operated system will also have a three-way illuminated status display unit which shows what status the system is currently in. These states are ‘automatic/manual mode’, ‘manual only mode’ or ‘gas has been discharged’. These units should be located at each entrance to the protected area to inform and protect building occupants who would enter the area.


A wet chemical system is a specialist active fire protection measure specifically to deal with hot oil and therefore commonly used to deal with potential deep fat fryer fires. Such systems can be relatively small and localised, such as for use in a commercial kitchen or on an industrial scale for use in situations such as large scale food production.


The wet chemical system will contain similar saponification agents to those used in Class F fire extinguishers, such as those chemicals based on nitrogenated derivatives and ammonium salts of phosphoric acid, hydrocarbon and fluorinated surfactants in aqueous solution. The extinguishing medium has a chemical action which forms a thick blanket of foam on cooking oil fires to subdue the flames, this foam also prevents re-ignition.


Further guidance on use of wet chemical systems can be gained from LPS 1223 (link to pdf) or UL 300, an American publication, Standard for Fire Testing of Fire Extinguishing Systems for Protection of Commercial Cooking Equipment, which is purchasable online.


In Part 27 of this series, we will be looking at Powder Systems and Aerosol Systems, both of which have specific uses. 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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