Mist is defined as a large mass of water vapor in the air consisting of fine drops of water, or a fine spray of liquid.

Following the CEN/TS 14972 definition, watermist is a water spray for which the 90% of the total volume of liquid (Dv0. 90) is distributed in droplets with a diameter smaller than 1000 microns at the minimum design operating pressure of the water mist nozzle.

A water mist system uses water mist to control, suppress, or extinguish fires by:

  • Cooling the flames and surrounding gasses through evaporation.

  • Displacing oxygen by evaporation.

  • Diminishing radiant heat by the small water droplets themselves.

Dual MIST  low-pressure misting system is a highly effective fire suppression method due to it's range of droplet sizes.

DualMIST utilises it's vast well of engineering knowledge encorporating complex methods to produce the unique nozzles and range in droplet sizes.  These range from small(<1000m) to large (jet spray).  Each of these size ranges play their own part in displacing the fire.

The larger droplets have the ability to penetrate the fire as the smaller droplets act like a gas causing the fire to suffocate and removing large amounts of heat energy particularly in places other suppression systems may struggle to reach (walls and ceilings).


 

droplet table.jpg

In the chart above you can see that the range of droplet sizes produced by the DualMIST system is in between that of sprinklers and high pressure systems.

With high pressure systems - a very fine mist/aerosol is produced which is very effective at heat suppression but not so good at high ceiling heights or in open areas as side draft can cause the vapor to be swept sideways away from the fire. With high pressure systems there is little surface wetting due to the droplets evaporating before they reach the fire or nearby heated surfaces.

With sprinkler systems there is a huge amount of surface wetting but very little heat suppression as there is very little mist produced and little to stop the heat spreading across the ceiling cavity by convection which is where most of the heat from the fire ends up. There is also no mechanism to stop heat transfer across the room from radiating burning/hot objects and even worse with sprinklers most of the water quickly ends up on the floor and is then effectively useless from a suppression point of view. The length of time the the water droplets spend in the air is a critical factor in heat suppression.

The fine droplets stay airborn for a prolonged period of time until most eventually evaporate and expand into inert gas (water vapor) displacing the air in the room and thus reducing the percent oxygen levels which in turn reduces the overall burn rate of the fire. The DualMIST nozzles use a combination of all the above methods to suppress the fire.

As you can see for a 2.5 height room there is an optimum range of droplet size to produce both effects. For higher height rooms the optimum range droplet size moves upwards accordingly.

Benefits of DualMIST

table.jpg
  • Reduced Water Consumption

By using up to 50% less water Dual Mist not only proves more cost effective but is also more    sustainable and friendly for the environment.

  • CPVC Piping

The use of CPVC piping increases flexibility during the installation as well as reducing the overall project costs as opposed to using steel.

  • Jet Spray

This is water projection expected to be seen in traditional sprinklers.  Dual Mist utilises this jet spray in order to propel the mist enabling it to cover the area and smother any potential fire.

  • Fine Droplets

Dual Mist uses fine droplets in order to supress the heat eventually turning into water vapour and reducing the oxygen levels which essentially suffocates the fire.

  • Coarse Droplets

It is the range of droplet sizes that make Dual Mist systems unique!  As well as suppressing the fire these coarser droplets begin by spraying high and then tend to run down the walls cooling them down and helping to prevent against further spreading.

  • Less Water Damage

Both high and low-pressure systems use less water than traditional fire sprinklers although with low-pressure in particular this is significantly less resulting in fewer damages to things like fixtures and furnishings overall.

What is Water Mist?