A description is given of the FIRE MOUSE TRAP (FMT - Flying Infrared Enhanced Manoeuvrable Operational User Simple Electronic Tactical Reconnaissance and Patrol) system for mapping forest fires, which was first used experimentally in Alaska in 1985. Forward looking infrared units (FLR) are slung beneath helicopters equipped with a navigation plotter unit which records the position of the helicopter every 2 seconds. The FMT infrared system can map the active fire edge through smoke and locate hotspots, even a burning log, for plotting directly onto a map or transparent overlay within minutes after the flight for use by ground fire control.