How does water mist work?

When water is driven through a specialised nozzle at very high pressures (in Automist's case around 80 bar), the water is atomised to produce a fine mist or fog. Water mist removes heat from the fire and displaces oxygen from the fire zone, resulting in fire control, suppression or extinguishment. The intention is to reduce the oxygen concentration around the flame, lower the temperature and lessen the radiative heat to such an extent that combustion can no longer be maintained, thus reducing damage and maintaining survivable conditions.

Traditional sprinklers mount on the ceiling, as a result, the water droplets have to flow (with gravity & momentum down) against the fire & smoke to reach the fuel, which flow upward. This also means when they activate they can also drag down the smoke layer on the ceiling reducing visibility.

In contrast, Automist through its side wall delivery is able to utilise the buoyancy of the fire plume to suck the mist in and suppress fires. Its lower position and early activation means it only needs 5.6 litres per minute to suppress fires which would require ten times as much with a traditional sprinkler solution. Archimedes in practice!

Figure 1: Relatively large droplets are denoted I, medium sized droplets are denoted II, very small droplets are denoted III. The situation denoted IV is when medium sized droplets are following entrained air and combustion products into the fire plume.