Uncooled thermal cameras using microbolometer focal plane arrays may be used in the long wave infrared (LWIR) for the optical detection of hydrocarbon gas leaks. The strong absorption of hydrocarbon gases in the LWIR may be used to advantage along with the LWIR optical transmission window of the atmosphere. Improvements in the detection algorithm and more robust electronic hardware have produced a gas imager that is well adapted to the detection of large hydrocarbon leaks. The new imaging system relies on a single set of filters to identify a growing list of gases, up to four of them simultaneously. The new detection algorithm reduces the incidence of false alarms by masking portions of the field of view. Because of the camera's long detection range (2 km) and wide field of view, the system is particularly suitable for the supervision of large industrial zones. Results from a field test of leaking gas at a refinery and natural gas processing facility are presented.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.