The LWF Blog
Fire Safety for Facilities Management Personnel – Fixed Fire-fighting Systems – Part 228
November 20, 2023 12:09 pmLawrence 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 227, LWF looked at how organisations may approach fire equipment and training of staff before considering the checks on fire extinguishing appliances. In part 228, we discuss fixed fire-fighting systems installed in a building.
A fixed fire-fighting or control system is one that is installed permanently in a building, or on an item of plant, for the purpose of controlling, suppressing or extinguishing fires. The systems may be either automatic or manual discharge of the fire extinguishing medium contained.
Extinguish, suppress and control are distinct terms that should be understood in order to ascertain the suitability of a system for purpose.
Extinguishment of fire – A sharp reduction in heat-release rate of a fire leading to a complete elimination of any flaming or smouldering fire.
Suppression of fire – A steady reduction in the heat-release rate of a fire, resulting in a lower level of controlled fire.
Control of fire – Fire growth is limited and the surrounding structure protected, e.g. by cooling of the surrounding objects, fire gases and/or by pre-wetting adjacent combustibles.
Fixed fire-fighting systems tend to be classified as either aqueous (water-based) or non-aqueous systems, according to the extinguishing agent used. However, the actual agent used must be the main focus as to suitability and the way in which it is discharged.
Water-based fixed extinguishing systems may be discharged as follows:
Sprinkler – For Class A fires in buildings
Drencher – For prevention of fire spread between buildings
Water Spray – High velocity – For extinguishing class B fires with liquids with high flashpoints
Water Spray – Medium velocity – For the control and extinguishing of Class B fires with low flashpoints and water miscible liquids (also protection of plant against radiation from an adjacent fire)
Fine Water Spray (mist) – For the control and extinguishing of Class A and B fires
Foam – Low Expansion – Class B fires
Foam – Medium Expansion – Class B fires
Foam – High Expansion – Class A fires
For non-aqueous fixed fire-fighting systems, discharges may be as follows:
Gaseous – Local application – Protection of a localized class A or class B risk within a larger volume
Gaseous – Total flooding – Protection against class A or class B fires throughout the entire volume of a protected space
Powder – Local application – Localized class B risks
Powder – Total flooding – Protection against class B fires throughout the entire volume of a protected space
In part 229 of this series, LWF will discuss automatic sprinkler systems. 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