The LWF Blog

Fire Safety for Facilities Management Personnel – Water Mist Systems – Part 246

April 2, 2024 10:50 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 245, LWF began to look at water mist systems. In part 246, we continue discussing water mist systems.

In recent years, the use of water mist systems in domestic and residential environments has been increasingly popular, due in part to situations where the space, weight and possible absence of water supply connection means a water mist option has proved attractive in terms of fire suppression.

The water mist systems designed for such applications may have been accepted by the enforcing authorities as compensation for a reduction in other fire protection measures, such as means of escape or to enhance protection for occupants at high risk of fire.

In a 2006 independent guide on water mist systems for residential buildings, published by the Building Research Establishment, basically said that while initial applications seemed to be effective, there was a lack of real evidence or expert interpretation on their use in domestic environments in the UK in the longer term. It also noted that, at the time, there were no British or European standards for components or systems.

Since that time, the following standards have been published:

BS 8458 Residential and domestic premises

BS 8489-4 Local applications involving flammable liquid

BS 8489-5 Protection of combustion turbines and machinery spaces up to 80m3

BS 8489-6 Industrial oil cookers

BS 8489-7 Low hazard occupancies (as defined in BS 8489-1 from Category I – III)

BS 8458 addresses domestic and residential applications, while the remainder listed are for commercial and industrial water mist systems.

BS 7273-5 is the code of practice for the operation of fire protection measures – Electrical actuation of watermist systems (except pre-action systems) and it relates to the interface between fire detection systems and water mist systems.

System design and technology for water mist systems varies. Some systems use a single fluid (water, often at high pressure) and some use dual fluids with added nitrogen to atomise the water at the nozzle. Liquid droplet size, velocity and distribution vary between manufacturers and the size of the equipment itself, along with water tank size and if it is connected to the water supply also vary depending upon intended application. Systems connected to the water supply in a way more like a traditional sprinkler system will be able to operate for much longer than a tank system.

In part 247 of this series, LWF will begin to look at Foam 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.

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