(FLIR) a hand-held or aircraft-mounted device designed to detect heat differentials and display their images on a video screen —note FLIRs have thermal resolution similar to infrared (IR) line scanners, but their spatial resolution is substantially less; they are commonly used to detect hot spots and flareups obscured by smoke, evaluate the effectiveness of firing operations, or detect areas needing mop-up This definition last updated 10/24/2008