Pool Fire Extinction by Remotely Controlled Application of Liquid Nitrogen

This article presents a technique for effective remote-controlled application of liquid nitrogen to fires. Application of the cryogen from a distance, by spraying through a nozzle, proved challenging as evaporation along the trajectory path of the jet reduces the quantity of the liquid reaching the fire. To the contrary, use of a remotely guided unmanned robotic vehicle to carry the hose to the fire and discharge the cryogen in the fire proved to be more effective. Upon contact with a pyrolyzing/burning surface or the ground, abrupt vaporization of the cryogen generated cold vapors that spread by gravity and blanketed the burning area. The pyrolyzing gases were inerted, the surface was cooled, air was separated from the fuel, and the fire was extinguished. To demonstrate this technique, experiments were conducted with pool fires of isopropanol. Fire extinction in these feasibility tests was fast and effective. (C) 2011 American Institute of Chemical Engineers Process Saf Prog 30: 164-167, 2011