The LWF Blog

Fire Safety Engineering for Design – Sprinkler Protection – Part 227

March 24, 2025 11:54 am

LWF’s Fire Safety Engineering blog series is written for Architects, building designers and others in the construction industry to highlight and promote discussion on all topics around fire engineering. In part 226, LWF looked at light and ordinary hazard risks. In part 227, we will begin to discuss high hazard risks.

A high hazard risk will be found in an industrial or commercial setting which has abnormal fire loads, likely due to one of the following:

• The processes carried out in the premises
• Storage of goods on the premises
• Method of goods storage and height to which they are stored

The risks are subdivided into one of three types of risk:

• High hazard process risks
• High hazard storage risks
• Special hazards (as defined in LPC Sprinkler Rules with BS EN 12845, incorporating what used to be TB217)

Where a high hazard risk is present in an occupancy, an unchecked fire on the premises would be likely to follow a fast to ultra-fast fire growth curve and result in an extremely high output fire. The fuel load is likely to be in excess of 1000 MJ^.m^-2 and all these factors combine to indicate a fire that the Fire Service would have trouble bringing under control.

Sprinkler installations can help achieve fire control, but not easily. For this reason, it is necessary to reduce sprinkler spacing and increase discharge densities and water supply duration periods.

In the case of storage risks, the variables should be considered, including the methods of storage, whether they are free-standing, palletised racks etc., the type of goods stored, packaging materials and the height to which the goods are stored.

It stands to reason that, just as each organisation is different and manages inventory, processes etc. in different ways, that a sprinkler system to mitigate the high hazard risks would need to be designed to suit that particular set of circumstances. This may comprise of a roof level sprinkler system, or a combination of roof sprinklers and sprinklers located within the storage racks.

Sprinkler systems may be ‘early suppression fast response’ (ESFR) and ‘control mode specific application’ (CMSA) sprinkler systems.

The third type of subdivided risk mentioned above – special hazards – consist of the following:

• Flammable aerosols
• Clothes in multiple garment hanging stores
• Flammable liquids in storage
• Idle pallets
• Non-woven synthetic fabric
• Polypropylene or polyethylene storage bins

In part 228 of LWF’s series on fire engineering we will discuss sprinkler heads. In the meantime, if you have any questions about this blog, or wish to discuss your own project with one of our fire engineers, please contact us.

Lawrence Webster Forrest has been working with their clients since 1986 to produce innovative and exciting building projects. If you would like further information on how LWF and fire strategies could assist you, please contact the LWF office on 0800 410 1130.

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.