Their arrival will mean smaller fire engines, smaller hoses and less water damage - a major problem for property owners.
High pressure guns are just one of several innovations expected to transform the London Fire Brigade in the next five years.
The highly compressed water removes heat from fires more efficiently and puts out flames more quickly.
The brigade's deputy head of research and development, Dave Towler, said: 'This atomised spray means we use less water. As the size of appliances is dictated by the amount of water, we could have smaller fire engines - a big advantage in a city like London.'
Two Hungarian manufacturers are developing products using compressed air to create a fine spray. One is making a high pressure pump, the other a pulse gun.
The brigade is also running trials with new lightweight breathing apparatus cylinders made of carbon fibre.
Two of these weigh 12 kilograms, lighter than the single cylinder carried by London fire crews. They give 70 minutes breathing time, compared with 46 minutes at present.
'That can make a lot of difference when fighting a fire on the London Underground, for instance,' said Mr Towler.
A third innovation expected to be introduced is a thermal image camera fixed to a fireman's helmet.
This can help a fireman to see through a smoky building and spot trapped victims faster. Video pictures are relayed to senior fire officers outside who can then direct crews more efficiently.
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