A water mist system uses water and compressed air to generate a very fine water droplet. These systems use significantly less water than standard sprinkler systems. Water is an outstanding fire suppression agent due to its high heat capacity and latent heat of vaporization. The Fike Micromist system nozzle uses a plate to slice the small jets of water that flow through the nozzle orifice. The resulting water mist contains a variety of droplet sizes. The larger droplets produced by the nozzle provide the necessary energy and momentum to carry the smaller droplets to the base of the fire where the mist vaporizes and extinguishes the fire. The simple theory behind this development is that a large amount of small droplets have a greater surface area than the same volume of large droplets, therefore absorb more heat.
Water mist systems extinguish fires using the following basic principles:
Cooling – As the mist is converted into vapor it removes heat from the fire source.
Inerting – As the water mist turns to steam it expands approximately 1700 times, forcing oxygen away from the flame front, thus denying it the oxygen necessary to support combustion. (localize inert environment)
Wetting – Primarily for incidental Class A fires; wetting of the surface helps extinguish the fire as well as contain it.