Vivek Vijay, Certification Specialist with Emirates Safety Laboratory, explains the importance of third-party certification for water mist systems
When we hear about a water mist system, multiple questions arise regarding its reliability, durability, effectiveness parameters on various classes of fires, system maintenance costs, how it can replace other suppression agents – the list goes on. Some still perceive water mist to be an ineffective or antiquated fire suppression/protection system compared to other suppression agents like foam, clean agents, or dry and wet chemical systems.
In recent years, there has been solid progress in water mist system technologies with various new brands entering the market with their unique designs, better extinguishing abilities, improved reliability, and advanced durability. It is time to reconsider and explore water mist systems, the benefits these types of systems can provide and explore insights into how these systems support sustainability, and water conservation, and contribute to impacting less on the environment.
NFPA defines water mist systems as fire suppression systems that use ‘very small’ water droplets to extinguish or control fires. These droplets are more efficient and effective in containing fires over standard sprinkler systems due to the increased cooling effects, oxygen displacement capability, and pre-wetting function that the droplet size and distribution provide.
Other benefits of water mist systems over standard sprinkler systems are they require less water and operate via reduced pipeline sizes. Water mist fire protection systems can be either a single fluid (water) or twin fluid (water & atomising media) system.
A water mist system, sometimes referred to as fog or ultra-fog water mist system, utilises water as a medium, like conventional sprinkler systems, for containing and extinguishing the fire. So why consider a different system that uses the same medium for fighting and suppressing fires?
To answer this, we need to explore various considerations, including the difference between a water mist system and a traditional sprinkler system, whilst seeking to understand the reliability and effectiveness of water mist and, for selection, we need to consider specific hazards and occupancy needs.
It is the revolutionised design of a water mist system where the water droplet size is significantly reduced to an extent where it is discharged in the form of fine mist from a discharge device. The mist droplet absorbs enough heat for it to convert from liquid state to steam, it expands, and when the water molecules expand as steam, it eliminates oxygen molecules from the burning particulate.
Also, with respect to the consumption rate of water, a water mist system uses 50 to 90 per cent less water as compared to a traditional sprinkler system. Again, the merit of the water mist system is not only limited to controlling the room temperature and converting droplets to steam, thus suffocating the fire, but also in its ability to reduce water damage as compared to traditional sprinklers. With that, the water mist system proves to be more efficient on electrical fires as well as occupancies with valuable items that require as little water damage as possible.
Setting the standard
Now the question is, how can a water mist system be considered reliable for the protection of specific applications and specifically protected area volumes? If a manufacturer/distributor approaches you with a conformity certificate for their water mist system against NFPA 750 standard, can it be accepted or not?
The answer is no. Why? Because NFPA 750 standard provides a guideline for the minimum requirements for the design, installation, maintenance, and testing of water mist systems. As mentioned in the scope section of the NFPA 750 (2023 edition), ‘This standard does not provide definitive fire performance criteria, nor does it offer specific guidance on how to design a system to control, suppress, or extinguish a fire’.
Then what are the standards available in the market for getting water mist systems tested and certified? Is certification granted for the entire system or for individual components? Is there a unique comprehensive standard for water mist systems?
Third-party certification agency, such as Emirates Safety Laboratory (ESL), can support end users with customised evaluation program for the specific water mist system based on the individual requirements as per the FM 5560 standard.
A third-party conformity assessment body (CAB) will work case by case and provide customers with a tailored assessment program that will be acceptable local authorities. When it comes to fire test protocols, they are common and required for all water mist systems. Certification agents such as ESL will be able to specify the range of components and fire tests that need to be conducted for the proposed system.
ESL’s certification assessment program is not limited to component evaluation and fire test protocols. It also includes a peer review of the manufacturer’s design, installation, operation, and maintenance manual, ensuring the proposed water mist system is designed for the specific application/hazard.
A detailed technical study about installations should also be carried out and evaluated to determine whether the proposed installation can achieve maximum effectiveness. When it comes to operation and maintenance, the third party should ensure that the proposed system is user-friendly and easy to maintain, and many such technical aspects ensure the proposed system is appropriate and suitable for the specific environment, hazard and applications.
Third-party certifier exists to support manufacturers or their representatives to obtain accreditation for either individual component component assemblies or the entire water mist system itself. For example, ESL will focus on the customer’s targeted market and our evaluation program includes the local regulations/requirements. We will also help to identify whether the individual component needs to be included in the certification program or not.
By holding a third-party certificate of conformity for your water mist system, the product is demonstrably capable of combatting almost all classes of fires. Certified water mist systems can now displace traditional sprinklers for Class A fires, foam concentrates and dry chemicals from Class B fires, clean agents and carbon dioxide from Class C fires and finally, wet chemicals from Class K/ Class L fires.
A new perspective
Over the past decade, various research shows that a water mist system is as effective as a foam system even though it does not create a complete cover of a blanket over the hazard. It can suppress fire by displacing oxygen with the steam production and needs to stay for a period of time to prevent re-ignition. The case is very similar when it comes to an alternative to dry chemical systems and clean agent systems.
Studies showed that due to the droplet size, a water mist system causes very little damage to equipment, reduced respiratory issues, relaxed evacuation of people, easier residue cleaning, etc., and when compared to the clean agent and dry chemical systems, associated costs can be significantly less for water mist system.
The most important component of a water mist system is its high-pressure pump system. Third-party certifiers such as ESL can provide individual certification for high-pressure pumps and their associated accessories. An evaluation program for water mist pump certification will be set out based mainly on the type of pump and its targeted market and the assessment will provide conformity on the product and verifies its performance, durability, reliability and its suitability.
Another major component of a water mist system is its discharge nozzles which contain two or more orifices designed to produce and deliver an atomized water spray. Nozzles can be designed to operate independently of other nozzles, as a group of nozzles or as a combination of two or more.
Certification offers assurance that the proposed nozzle is suitable for the specific requirements. This can be achieved by undertaking a peer review and evaluation, executed by undertaking a detailed assessment of the various test results understood from the test reports that were conducted in accordance with the CAB’s test plan.
The conformity certificate issued by ESL will better position the manufacturer to access more markets and geographies, and at the same time, end users can trust and rely on the proposed system design, assured performance and fire rating criteria.
Emirates Safety Laboratory can provide a certificate of conformity to the water mist system or its individual component and component assembly through its tailored assessment plan as per the FM 5560 standard and other local regulations enabling more user-friendly and reliable water mist system products to be introduced into the market.
This article was originally published in the September edition of IFSJ. To read your FREE digital copy, click here.