Water mist systems are an active fire protection solution recognised by numerous local regulations and international standards, including NFPA 750 (National Fire Protection Association) and EN 14972 (European Standard).
This method differs from conventional sprinkler systems in its ability to pressurise water to between 70 and 200 bar, in other words. at high pressure, and consequently generate droplets of less than 1000 microns. These micro-droplets rapidly cool the fire and displace oxygen due to the vapour produced, therefore achieving effective extinguishing or suppression.
Amongst the most important specifications set by regulatory standards for the use and installation of water mist systems, are: definition of the scope, determining whether the system must eliminate, control or suppress the fire; types of systems, including dry pipe, activated by fire detection, and wet pipe, which operates by automatic sprinklers; design parameters, such as the type and location of sprinklers, design pressure and minimum flow rate, among others; system support, a critical factor due to the high working pressures (from 150 to 200 bar); and minimum discharge duration, depending on the type of risk and applicable regulations.
The advantages of these systems include cooling efficiency, thanks to the water evaporation process; reduction of water damage in sensitive areas such as archives, museums, libraries, historic buildings and server rooms; safety for people and the environment, as, unlike extinguishing gases such as halons or COâ‚‚, water mist does not create toxic hazards and does not require sealed enclosures; ease of recharge and maintenance, with simple and inexpensive replenishment after activation; and water sustainability, as water consumption is significantly lower compared to conventional sprinklers – as water mist protects up to 10 times more surface area than a traditional system.
However, these systems also present limitations and challenges. One of them is the complex technical design they require, as they are not standardised and must be adapted to the specific characteristics of the risk and the applicable regulations. They also present limitations in open spaces, where micro-droplets tend to be dispersed, which reduces their effectiveness. Finally, the high cost of installation and maintenance, due to the advanced technology and specialised components required, is also a limitation.
By Juan Carlos Soria, Senior MEP Engineer in Amusement Logic’s Architecture Dept.
