In designing fire protection for critical assets in demanding environments, traditional sprinklers and gaseous systems are not always the best fit. Water mist fire suppression has emerged as an effective alternative that minimises water damage, supports life safety and offers strong environmental performance, particularly in specialised and high-risk applications.
ASP Fire CEO Michael van Niekerk says, “Clients increasingly want fire protection that is technically robust and sensitive to their operations. 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.”
Van Niekerk explains that 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.
Conventional sprinkler droplets are much larger. The smaller droplet size in water mist systems increases the total surface area of water exposed to heat. As the droplets absorb heat and rapidly evaporate as 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 extinguishing, with a fraction of the water flow of traditional sprinkler systems. This 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,” says van Niekerk. “We get the cooling and oxygen displacement benefits of water, but with much lower volumes and a more controlled impact on equipment, structures and contents.”
Where water mist is most effective
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, and it does not require gas-tight enclosures as many clean-agent systems do.
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. Many cultural and public facilities are moving away from chemical agents and large-water-volume systems due to concerns about environmental impact and damage to irreplaceable collections. Carefully designed water mist systems have been deployed in libraries, heritage structures and archives as they use significantly less water and offer gentle, localised suppression.
Fourth, high-end hospitality, commercial kitchens, and specialist industrial risks. Water mist has gained traction in hotels, office buildings, industrial fryers, and special hazard areas where occupant safety and rapid return to service are crucial. In some jurisdictions it has become a preferred solution for commercial cooking areas and other high-heat, high-grease environments.
In the African context, ASP Fire also notes the role of water mist in mining and heavy industry. “In mining environments, traditional powder systems can compact and fail, and visibility after discharge becomes a major problem for safe evacuation,” says van Niekerk. “Water mist, often in combination with foam for fuel hazards, can provide effective suppression with better visibility, faster clean-up and improved safety for personnel.”
Water mist in rational fire design
For ASP Fire, water mist is part of a broader shift towards rational, performance-based fire safety engineering. South Africa has seen several high-profile fires in complex buildings and infrastructure, from central business district fires to critical electrical and public facilities, prompting renewed scrutiny of suppression strategies.
“Rather than defaulting to a single technology, we design from the risk outward,” says van Niekerk. “Where analysis shows a high-value, high-consequence assets, limited water availability or a need to keep water damage to a minimum, water mist often emerges as a suitable solution.”
He emphasises that the appropriate system selection must be supported by detailed hydraulic calculations, fire modelling, component certification and, where appropriate, full-scale fire testing in line with NFPA 750 and other applicable standards.
For more information visit: www.aspfire.co.za
