The LWF Blog
Fire Safety for Facilities Management Personnel – Sprinkler Installation Design – Part 235
January 15, 2024 12:43 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 234, LWF looked at sprinkler installation design principles. In part 235, we discuss the density of water discharge and assumed maximum area of operation (AMAO) for ordinary hazard occupancies, as well as typical occupancy classifications.
Ordinary and high hazard occupancies are subject to further divisions of classification within BS EN 12845 Fixed firefighting systems. Automatic sprinkler systems. Design, installation and maintenance.
For ordinary hazard subcategories (ordinary hazard groups I, II, III and IV), the minimum design density in the most hydraulically unfavourable area of the installation is the same (5mm/minute), but the AMAO ranges from 72 m2 to 360 m2 depending upon the hazard group.
The kind of premises which would normally fall under the ordinary-hazard occupancy heading are industrial and commercial premises where there is less chance of rapid fire development based upon the nature of the fire load and method of storage.
Many office buildings (unless high-rise) would fall under ordinary-hazard group I, provided there are no major storage areas involved.
A typical factory producing light metalworks may be classified as an ordinary hazard group II; a department store may be ordinary-hazard group III, while a theatre would be classed as ordinary-hazard IV.
BS EN 12845 gives typical examples of ordinary-hazard occupancies and their groupings, but appropriate and accurate classifications can vary considerably even given the type of business function taking place on the premises. Insurance company opinions may prove to be different than the examples given in BS EN 12845. For this reason it’s important to consult with the insurer at the design stage of any sprinkler installation.
In part 236 of this series, LWF will talk about high-hazard occupancies, where the risk of fast-spreading fire is greater than ordinary-hazard occupancies and the sprinkler installation is tasked with a more significant challenge. 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.