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July 13, 2021


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Water mist systems

Water mist systems: What to consider and why third party testing is essential

Jade Musto, Head of Suppression System Testing at the Fire Protection Association (FPA), provides some clarity on the benefits of water mist systems and explains why it is crucial that those being specified and installed by fire safety professionals are third-party certified.   

Water mist systems can play a critical role in preventing the spread of fire and are highly effective if used correctly. As the name suggests, the systems work by spraying small droplets of water, which is done at relatively high pressure. These systems work by lowering the temperature and reducing the oxygen concentration to the extent that combustion can no longer be maintained, and the flame is extinguished.


Because water mist systems discharge less water than traditional sprinkler systems, they are typically used in residential or domestic premises, however they are becoming increasingly common in commercial buildings such as offices, schools and leisure facilities.

When it comes to maximum effectiveness, however, it is important that they are designed with the exact environment in mind and are tested prior to installation. For building owners and those responsible for fire safety within a building, seeking third-party testing is a critical step in ensuring the proper and safe use of water mist systems.

Water mist vs sprinkler systems

Water mist systems offer many benefits compared to standard sprinkler systems. For example, they do not rely on the larger water supplies needed to support sprinklers and use smaller pipes and components, so take up less space. This makes them an appealing fire protection method in environments where it would be difficult to accommodate a larger system, and this includes retrofits where installers need to be careful not to encroach on existing pipe networks.

As a lower volume of water is used to extinguish the fire using water mist systems, they are also likely to have a lesser impact on a building’s contents and be easier to clean up. This makes them a good fit for residential properties, where residents may be left without essential appliances or furniture, and face large costs in replacing them.

However, while water mist is particularly effective at supressing fires in buildings which are compartmentalised, it does not work well in highly ventilated spaces, as the droplets of water can be dispersed by factors such as air conditioning or open areas between floors.

The key considerations for building owners

Design with the building in mind

One of the biggest points of difference between a water mist and sprinkler system is that water mist systems must be designed with the exact environment in mind, making every installation almost entirely unique. This is because there are fewer appropriate standards or certification schemes to rely on, while water mist components are often bespoke to individual manufacturers and are not interchangeable.

Building owners and those responsible for fire safety should therefore engage with a third party that has the knowledge and experience to carry out a thorough inspection pre-installation, as well as advise on next steps and conduct regular maintenance. This is the only way to ensure systems will perform as intended should a fire occur.

BS 8458 water mist testing

Because water mist systems are so dependent on their environment, it is critical that the devices are tested prior to their installation. The FPA is passionate about improving fire safety standards across the built environment and is leading the way as one of the first UKAS-accredited fire testing facilities in the UK to offer testing on residential and domestic water mist systems to BS 8458: 2015.

This test provides residential and domestic system designers and installers with the assurance their system has been tested to the highest standard and will perform as intended should a fire occur when installed under the test conditions.

Nozzle testing

Regular testing of water mist nozzles will help ensure that the systems continue to do their job in the event of a fire. This should only be carried out by an independent third party and not the system owner, manufacturer, installer or maintainer as this means it will be impartial and unbiased. Removing the nozzles should also only be done by a trained professional as the water pressure can be so high it could cause serious injury and health risks.

The FPA recommends as best practice that nozzles are removed and sent for testing after 10 years of service and tested every five years after that. This supports the recommendation of NFPA 25 Standard for the Inspection, Testing, and Maintenance of Water-Based Fire Protection Systems.

Water mist – and other automatic fire suppression systems (AFSSs) – can be instrumental in minimising the risk of fire and fire spread, helping to preserve life and building safety as well as limit the potential knock-on effects for communities. While not as established as sprinklers, water mist is a promising technology and can be especially effective in certain scenarios and building types.

Despite this, they often undergo less rigorous testing than sprinklers, which is a mistake – especially as each system can vary drastically from one another. Instead, building managers and those involved in the provision of fire safety should be seeking support from a certified third party to ensure the systems can protect people and the property in the event of a fire.

Find out more information and advice from the FPA about water mist systems.

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