To compare the efficiency of mist extinguisher with electric heating (OVA-93) using for fire suppression of class B fires in accordance with national and international standards, the experiments have been performed. Effects of the way of water aerosol feed in the zone of flame combustion and the time of free burning out of fire on the efficiency of the extinguisher have been examined. The evaluation for coefficients of water use according to optimal water supply conditions has been performed.