An open path gas detector system called a "gas detector" continuously monitors the levels of a flammable hydrocarbon gas at a range of 5 to 200 meters. Continuous monitoring of flammable hydrocarbon gas concentrations in the range of 0 to 1,5 LEL/m, 0-2,5 LEL/m, and 0-5 LEL/m over a distance of 5 to 200 meters are provided by the TGAES hydrocarbon gas detector, an open path infrared gas detector.