Use of Seawater for Fighting Electrical Fires

Abstract : The use of both fresh water and seawater for combating fires involving energized electrical equipment has been studied to establish safe approach distances for fire fighters. A variety of nozzles were tested at source voltages of 120 V ac and Dc, then up to 4160 V ac using both fog and straight stream patterns. The nozzles were attached to a moveable cart and the stream directed at a target grid which was energized at the test voltage. The current passing through a 500 ohm resistor connected to the nozzle, which was used to simulate the fire fighter, was measured as an indicator of electrical hazard. The cart was backed away in one foot measurement until no current passed through the resistor. It was found that with seawater, fog patterns were significantly less hazardous with respect to electrical shock than straight streams. In fact, fog patterns from standard Navy fire fighting fire fighting nozzles presented no shock hazard at distances greater than three feet. By contrast, straight stream patterns required up to 22 feet separations before the zero current point was reached. The safe approach distance varied with the nozzle type, even at the same flow rate. Fresh water streams were shown to require significantly shorter distances than seawater to produce most physiological effects, but the distances required to produce zero current flow were not appreciably different.