Systems, cameras, and software for performing optical gas imaging using thermal imaging. Processors are programmed with instructions for a method of detecting gas that includes creating a filtered background image, a filtered foreground image, and optical gas image data, and generating a display image. The filtered background image and filtered foreground images may be created by combining infrared image data from a plurality of images captured by an infrared camera module using filtering processes. The optical gas image data may be created by comparing the filtered background image and the filtered foreground image. An image may be generated that includes the optical gas image data for presentation on a display.