Evaluation of New Liquid Fire-Extinguishing Agent for Combustible Metal Fires
A new liquid fire-extinguishing agent for combustible metal fires was evaluated. Aircraft rescue fire fighters may confront metal fires, such as magnesium and titanium, in aircraft brake assemblies, landing gear components, aircraft engines, and other structural components of aircraft. A combustible metal on fire could be a possible ignition source or a continuing source of ignition in an aircraft fire. The standard method for extinguishing combustible metal fires consists of using sodium chloride dry powder to smother the burning metal.
This evaluation determined the optimum chemical formulation and best extinguishing method using FEM-12 SC in hand-held extinguishers during the Federal Aviation Administration (FAA) Aircraft Rescue and Firefighting (ARFF) Research Program’s combustible metal fire-testing protocol. A further evaluation included aquatic-toxicity testing of FEM-12 SC, and the extinguishing performance of FEM-12 SC compared to sodium chloride dry powder in accordance with the parameters set forth in the American National Standards Institute/Underwriters Laboratories Incorporated 711 “Rating and Testing of Fire Extinguishers,” Section 10.2, Magnesium Fire Tests, Section 10.2.28, Magnesium Casting Fire Tests.
The tests conducted by the FAA ARFF Research Program determined optimum chemical formulation, FEM-12 SC, and the best extinguishing method using 240 pounds per square inch, high-pressure extinguishers in a straight-stream configuration. The aquatic-toxicity test results showed that FEM-12 SC was tested at 675 parts per million (ppm) median lethal concentration and was within the acceptable accuracy range of greater than 500 ppm. The extinguishing performance comparison results showed that sodium chloride extinguished a magnesium fire in an average of 102 seconds, twice as fast as FEM-12 SC. However, it created a potential long-term fire hazard due to its inability to cool the metal, which could redevelop into a fire if the sodium chloride-covered metal was disturbed. FEM-12 SC provided better cooling than sodium chloride so that the magnesium could be handled with bare hands within minutes of extinguishment. However, when FEM-12 SC came in direct contact with the burning magnesium, violent flare ups of the fire and flying magnesium sparks created potential fire hazards. Once the fire was extinguished, the fire hazards were eliminated.
DOT/FAA/AR-TN06-26
Authors: Keith Bagot & Nicholas Subbotin