The LWF Blog

Fire Safety for Facilities Management Personnel – Sprinkler Installation Design – Part 236

January 22, 2024 12:15 pm

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 235, LWF discussed the density of water discharge and assumed maximum area of operation (AMAO) for ordinary hazard occupancies, as well as typical occupancy classifications. In part 236, we talk about high-hazard occupancies, where the risk of fast-spreading fire is greater than in ordinary-hazard occupancies.

High-hazard occupancies are premises in which the processes undertaken or the nature, amount or type of storage are such that there would be a greater challenge to the sprinkler system installation.

High hazard risks are divided into four main areas:

• Process hazards
• High-piled storage hazards
• Potable spirit storage hazards
• Oil and flammable liquid hazards (usually would require special protection)

The areas are further divided under each heading. There are four types of process hazard, for which the densities for the sprinkler system vary between 7.5 mm/minute to 12.5 mm/minute.

Three of the types of process hazard have the same AMAO, but the minimum density of discharge varies. The fourth type isn’t commonplace, but includes firework production. BS EN 12845 recommends each building of the fourth type be provided with complete ‘deluge’ protection. Such systems consist of open heads which discharge water over the entire area when the installation is activated by fire detectors.

A high-piled storage hazard building is usually a warehouse. The definition of high-piled varies according to how the commodity in question is stored and the type of stored goods. The goods themselves are classified into four different categories, according to the level of fire hazard they represent.

The minimum design density and AMAO are related to the storage height. The premise is that some forms of goods are not high risk unless they are stored above a certain height.

Some categories and heights of high-hazard racked storage are not sufficiently protected by ceiling mounted sprinklers and require intermediate sprinklers within the storage racks.

In part 237 of this series, LWF will continue to discuss high-hazard occupancies, classifications and the resulting design of the sprinkler protection installation. 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.