Fireworks manufacture a unique fire suppression system that uses atomised high pressure water to extinguish a fire by rapid cooling at the flame front. The water droplets dramatically reduce the temperature in the room and also absorb smoke particles. Their systems are already installed in more than 100 prisons in the UK where they are installed primarily to tackle cell fires.  The principle, however, can be used in much larger situations.

Custodial Review spoke to Derek Killaspy to find out more.
CR    Much of the equipment you have fitted into prisons has been concerned with extinguishing cell fires or on landings which tend to be small blazes in a confined areas.  What I would like to discuss is the application of your technology in areas where larger blazes can occur, such as a kitchen.
DK    The worst fire that can happen in a kitchen is a deep fat fryer blaze. Hydramist is ideal for these risks because of how it puts out fires in hot oil. The system works by using the heat of the fire to convert the atomised water into steam. This both rapidly reduces the temperature of the oil and creates an oxygen free area at the flame front and therefore quickly and efficiently extinguishes the fire..  Because the hot oil is quickly cooled re-ignition of the fire is prevented.
CR    Usual advice is never put water on a fat or oil fire, so why would you spray water onto an oil fire?
DK    The reason for the advice is that water is heavier than oil and it expands over 1100 times when it turns from water into steam. Oil usually cooks at 180 degrees and has a huge amount of latent heat due to the volume of oil in the fryer. so water poured into hot oil sinks under the surface then expands so quickly it’s almost an explosion. This causes the oil so be showered over a large area, usually including the person who poured the water into the oil.
What the Hydramist system does is to spray atomised water onto the flame front and heat above the oil. The water droplets do not sink under the surface as they are constantly converted to steam above the oil until the temperature reduces to below 100 degrees C. So the atomised water never gets under the surface of the oil whilst a danger of it turning to steam exists. Therefore it cannot cause an explosion.
The reason the system works so effectively is because the atomised water is turned to steam at the flame front and so removes heat from the fire and oil, it then condenses and can fall back onto the blaze, repeating the cooling process.
The atomised water never gets under the surface of the oil whilst a danger of it turning to steam exist, therefore it cannot cause a ‘fat explosion’.
CR    Is there a limit to the size of fryer you can protect with this system? I ask because the huge amount of heat stored in large amounts of oil would take some time to cool.
DK    We are presently protecting a whole range of commercial fryers of the type you would see in fast food outlets and restaurants, we are also protecting fryers in factories that are several metres long, and contain several tons of oil. So the answer to your question is that there is no limit to the size of fire the system can extinguish.
CR    The amount of heat stored in hot oil must limit the speed at which fires are extinguished, as there is a lot of heat to vaporise the water droplets into steam. So how long does it take to put out an average commercial chip fryer?
DK    Oil that has caught fire is probably at a temperature of 240 degrees C and with one nozzle working it takes about 2-4 seconds to extinguish the flames and less than 1 litre of water, and about 2 minutes until the oil temperature is down bellow its flash point.
CR    The nozzle; is this on a hand held device similar to the cell fighting equipment you supply or is it a pre installed and plumbed unit?
DK    It’s preinstalled and plumbed because the philosophy behind our system is that the person who is using the fryer probably isn’t a trained fire-fighter.  We do not recommend that anything hand held, like a fire blanket or an extinguisher, is used as the person has to get close to the fire and risk possible injury. Our system is completely automatic, though it will also have a manual start placed some distance away. In all the testing we have done in conjunction with (Building Research Establishment , BRE) we have proven that our automatic system is quicker and more efficient than any other system for this risk.
CR    Where is this nozzle positioned and how is it triggered? Are there any warning signs?
DK    It’s approximately 1.3 meters above the fryer, so it’s out of the way of the operator and cannot cause injury. There is a heat sensitive bulb in the nozzle and when it reaches a pre set temperature the bulb breaks and this triggers a flow of water and the pump to activate. The temperature at which the bulb breaks can be varied, but for a typical fat fryer protection system it will operate at 93 degrees C.
CR    Playing devils advocate now. You have a nozzle 1.3 meters above a large pan of 180 degree oil. What happens if it goes wrong and squirts a stream of cold water straight into the fat right in front of the operator?