PROTECTING critical assets in demanding environments with traditional sprinklers and gaseous systems is not always the best option. Water mist fire suppression has emerged as a highly effective alternative that minimises water damage, supports life safety and offers strong environmental performance, particularly in specialised and high-risk applications.
“Clients increasingly want fire protection that is both technically robust and sensitive to their operations,” says ASP Fire CEO Michael van Niekerk (pictured). “Water mist systems give us another proven tool in the engineering toolbox, especially where conventional sprinklers, foam or gas systems present unacceptable trade-offs in terms of water damage, downtime or enclosure integrity.”
Smaller droplets
Water mist systems are water-based fire suppression systems that discharge very fine water droplets through specially engineered nozzles at low, intermediate or high pressures. According to NFPA 750, the Standard on Water Mist Fire Protection Systems, water mist is defined as a spray in which 99% of the water volume is in droplets smaller than 1 000 microns in diameter at the minimum operating pressure.
By comparison, conventional sprinkler droplets are significantly larger. The much smaller droplet size dramatically increases the total surface area of water exposed to heat. As the droplets absorb heat and rapidly evaporate to steam, the system cools the flames and hot gases, displaces oxygen immediately around the fire and reduces radiant heat transfer.
The result is fast fire control or extinguishment, with a fraction of the water flow of traditional sprinkler systems, which in turn reduces collateral water damage, clean-up time, and business interruption.
“From an engineering perspective, water mist allows us to design tightly focused suppression solutions,” explains Van Niekerk. “You get the cooling and oxygen displacement benefits of water, but with far lower volumes and a more controlled impact on equipment, structures and contents.”
Applications
Water mist is not a universal replacement for all types of fire protection. It is most effective in well-defined, often enclosed or semi-enclosed hazards where the spray pattern can be engineered and validated for the specific fire risks.
International research and field experience highlight several core strengths. First, machinery spaces and engine rooms. Water mist is widely used in machinery spaces on ships, turbine enclosures, and generator rooms to tackle Class A (solids) and Class B (flammable liquids) fires.
The technology provides rapid knock-down with less thermal shock and corrosion risk than deluge systems, while avoiding the need for gas-tight enclosures required by many clean-agent systems.
Second, data centres, control rooms, and IT facilities. Fine droplets cool hot surfaces, inhibit fire spread and limit damage to equipment. Although water mist is not intended to penetrate sealed cabinets, it is effective at stopping fires from spreading beyond the point of origin, and reinstatement is often quicker than after a conventional sprinkler discharge.
Third, heritage buildings, libraries, archives and museums.
