Advanced IR emitters and sensors are under development for high detection probability, low false alarm rate and identification capability of toxic gases. One of the most reliable techniques for gas identification is Absorption Spectroscopy, especially in the Mid-and Far Infra-Red, where most molecules exhibit their strongest roto-vibrational absorption bands. A compact non dispersive infrared multi-spectral system is here presented, designed and developed for security and environmental monitoring applications. It utilizes a few square millimeters thermal source, a novel design multipass cell, and a smart architecture micro-bolometric sensor array coupled to a linearly variable spectral filter to perform toxic gases detection and identification. Preliminary tests for sensitivity and selectivity are undergoing using mixtures of ammonia and ethylene. Detection capability down to tens of ppm has been demonstrated. Possible improvements through the implementation of open path and hollow-fiber based sensors are discussed.