ATIS Company is developing a new optical remote sensor based on the GALAAD worldwide patented multispectral imaging technology registered in 1998. The developed prototype has demonstrated its capabilities as an infrared imaging spectrometer as it allows real-time remote detection, monitoring and localization of hazardous gas plumes. Based on a novel concept of imaging spectrometer, this technology uses an un-cooled IRFPA (ULIS 320 x 240 bolometer) to reduce significantly the production and running costs of the device. The core of the GALAAD technology is a dynamic continuous spectral filtering mechanism, which, opposite to standard spectrometers, builds an entire spectrum for each pixel with a spectral resolution down to 25 nm. This technology works for any gas having an absorption spectrum in the sensitivity band of the sensor (here 7 - 14 micron region). The processing of the resulting multi spectral images allows the detection and identification of the gases present in the atmosphere using their specific infrared signature. The concentration is quantified and overlaid directly on the infrared image to monitor the site in a clear and intelligible way.