A commercial Fourier transform interferometer system has been installed in a van and used to make long-path absorption and single-ended emission measurements of gaseous pollutant concentrations at a variety of pollutant sources. The system covers the infrared spectral region from 650 to 6000 cm-1 at a maximum resolution of 0.06 cm-1. In the absorption mode, many gaseous pollutants can be detected at parts per billion levels over a one kilo-meter path. In the emission mode, warm gases exiting industrial stacks can be detected at parts per million levels. The temperature of the stack gases can be determined directly from the spectra. This paper describes the interferometer system and results of recent measurements of jet engine, brick kiln, gypsum pond, and industrial stack emissions.