The LWF Blog

Fire Safety for Facilities Management Personnel – Gaseous System Agents – Part 253

May 20, 2024 11:15 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 252, LWF discussed inert gases and halocarbons, as well as the relevant design codes. In part 253, we will discuss the remaining items on the list of components of a typical gaseous extinguishing system.

The automatic fire detection arrangement for a gaseous extinguishing system can involve the use of a separate self-contained automatic fire detection system. BS 7273-1 contains recommendations on the interface between the fire detection and gaseous fire extinguishing systems.

It may be that some systems only require a simple mechanical means of detection in order to automatically release the gas and this is sometimes seen in small CO₂ installations. The method of detection in these cases may comprise one or more fusible links located within the protected area. The links are attached to a tensioned wire and when the fusible link melts due to the temperature increase caused by fire, the wire tension is released, permitting a weight to fall. The mechanical discharge release control activates as the weight falls. Such systems would only be suitable for use in usually unmanned areas.

BS 7273-2 contains specific recommendations pertaining to mechanically actuated gaseous extinguishing systems.

Where an electrically-activated system is to be used, a manual discharge control is often provided which comprises a device requiring two actions (e.g. lift flap, break glass). These actions open or close an electrical circuit.

In the case of a manually-activated system, a mechanical pull handle is often provided.

Whichever device is used for activation, it would be sited just outside the exits from the protected area, allowing personnel to leave the area and then trigger the gaseous extinguishing system.

An electrically-operated system should have a three-way illuminated status display unit which indicates whether the system is in automatic/manual mode or manual-only mode. It also provides a warning if the gas has been discharged. This unit should also be located at each entrance to the protected area.

In part 254 of this series, LWF will talk about wet chemical systems and powder 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.