When it comes to protecting critical assets in demanding environments, traditional sprinklers and gaseous systems are not always the best fit. 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. “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.”
What is water mist fire suppression?
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.”
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, 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. 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 both 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 has also highlighted the role of water mist in mining and heavy industry. “In mining environments, traditional powder systems can compact and fail, while visibility after discharge becomes a major problem for safe evacuation,” notes van Niekerk. “Water mist, often in combination with foam for fuel hazards, can provide highly effective suppression with better visibility, faster clean-up and improved safety for personnel.”
How water mist fits into 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,” highlights van Niekerk. “Where analysis shows a high-value, high-consequence asset, limited water availability or a need to keep water damage to an absolute minimum, water mist often emerges as a very strong candidate.”
He emphasises that proper 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.
Advantages of water mist systems
When correctly designed and applied, water mist offers a combination of benefits that are difficult to match with other suppression technologies. The first is reduced water consumption and water damage.
Since the droplets are so fine and are used more efficiently, water mist systems typically operate at significantly lower flow rates than sprinklers. This reduces the volume of water that ends up on equipment, finishes and sensitive contents, and can ease demands on water storage and pumping infrastructure.
The second is enhanced life safety and tenability. By absorbing heat and limiting smoke production, water mist can extend the available safe egress time, improve visibility, and reduce the risk of flashover and backdraft in certain scenarios.
The third is environmental performance. Unlike halon and many legacy chemical agents, water mist relies on water as the primary extinguishing medium and therefore has no ozone depletion potential or long-term global warming impact from the agent itself. This aligns with international moves to phase down high-GWP clean agents under agreements such as the Kigali Amendment.
The fourth is resilience in ventilated or ‘leaky’ spaces. Gaseous systems depend on maintaining a minimum agent concentration for a specified period within a sealed volume. In highly ventilated genset rooms or plant areas, this can be impractical. Here water mist can offer a more robust solution in such environments, as it does not rely on enclosure tightness in the same way.
“Water mist is about using physics intelligently: smaller droplets, more surface area, better heat absorption and oxygen displacement, and a much more controlled impact on the assets you are trying to protect,” says van Niekerk.
Limitations and the importance of proper application
Despite its advantages, water mist is not a one-size-fits-all answer. Industry guidance stresses that there are scenarios where other technologies remain preferable. Large, open or very tall spaces with strong air movement may dilute the mist and reduce effectiveness.
Certain flammable liquid and gas hazards, or very rapid-growth fires in open process areas, may be better addressed by foam, dry chemical or gas systems, depending on the risk assessment. Where very deep-seated fires in bulk solids are possible, traditional sprinklers or specialised systems might offer better penetration.
“Part of our role as fire engineers is to resist the temptation to ‘force fit’ water mist into every project,” says van Niekerk. “We evaluate the fuel load, geometry, ventilation, occupancy, and business continuity requirements, and then select or combine technologies accordingly. In many cases, water mist is ideal. In others, it becomes part of a hybrid solution, and sometimes it is not the right choice at all.”
New developments and emerging applications
Research and innovation in water mist fire suppression have accelerated in recent years, both internationally and in markets relevant to South Africa. One key area is new-energy and battery-related risks.
Recent reviews highlight the potential of water mist, alone or in combination with gaseous agents, to manage lithium-ion battery fires, solar installations, wind turbines and biomass systems, thanks to strong cooling performance and reduced environmental impact.
Another frontier is advanced droplet engineering. Experimental work on fine water mist microcapsules and microfluidic nozzles is exploring ways to produce ultra-uniform droplets with predictable behaviour, improving both suppression efficiency and modelling accuracy.
System certification and component testing continue to evolve. Organisations such as UL and others are refining test protocols for pumps, nozzles, and complete systems to ensure reliable performance across a wider range of hazards, while the most recent edition of NFPA 750 clarifies definitions for gridded and twin-fluid systems and provides stronger guidance on inspection, testing and maintenance.
On the application side, recent industry commentary points to rapid growth in data centre deployments, mixed-use developments, and buildings where compartmentation for gas systems is impractical, but the owner wants to go beyond basic sprinkler protection.
“Looking ahead, we expect to see water mist specified more frequently in conjunction with intelligent detection, remote monitoring, and integrated building management systems,” revels van Niekerk. “For clients, the value lies in a fully engineered solution that combines fast detection, targeted suppression and clear, actionable information during and after an incident.”
ASP Fire is already applying lessons from international research to local projects. “We are increasingly asked to protect high-value electrical infrastructure, mining equipment, and complex commercial facilities under South African conditions of loadshedding, constrained water supply, and legacy building stock. Water mist, when correctly applied, gives us a powerful option to balance safety, asset protection and operational continuity.”
A strategic tool for modern fire risk management
Water mist fire suppression has matured from a niche technology into a mainstream option for a wide variety of specialised applications. Its ability to deliver fast, effective suppression, with reduced water usage and limited collateral damage, makes it particularly attractive for critical infrastructure, heritage, and high-value industrial environments across Africa.
“Every project starts with understanding the risk,” concludes van Niekerk. “Water mist systems are not a silver bullet, but in the right context they offer exceptional performance. When we integrate them into a rational fire-safety design, backed by proper standards, testing and maintenance, they help our clients protect people, assets and productivity in a world of increasing fire risk.”