Environmental monitoring with passive Fourier transform infrared (FTIR) spectroscopy offers an effective method for the identification and quantification of hazardous gas pollutants. Infrared spectroscopy reveals the spectral signature of the pollutant when there is a temperature difference between the pollutant and the background radiation, resulting in emission or absorption by the pollutant. The US Army has a lightweight standoff chemical agent sensor system that generates 1024-point interferograms. The interferogram, being nonstationary, has special features that develop as a function of time. Appropriate signal processing techniques enable real-time detection and can eliminate the need for background radiation references. An algorithm has been developed for the detection of gaseous pollutants/chemical agents with single- or multiple-peak spectra. It exploits the time-dependent spectral behavior and employs signal processing techniques to enhance the spectral signature of interest in both time and frequency domains jointly, thus facilitating detection. The algorithm has been successfully developed and tested, via laboratory and real data, for the single-peak spectral signature pollutant SF6; the signal processing concept has been extended to DEMP, DIMP, DMMP, and TEP as representatives of multiple-peak spectral signature pollutants. The algorithm software is written in the C language; the SF6 algorithm was implemented on the Motorola M96002 DSP chip for real-time processing studies.