For reducing environmental discharge of NOx below 1 ppm, the authors propose a minimum NOx emission system comprised of an absorption process that can concentrate low level NOx coupled with a de-NOx process. Adsorption of NO, especially in the range 0.5-20 ppm, for various adsorbents are studied with adsorption at ambient temperature and with desorption at 353 K. Phenol resin based active carbon is found to have excellent adsorption characteristics and can achieve almost zero emission of NO. It can reach a maximum adsorptivity of 2.5 x 10(-3) m(-3) . kg under the presence of O-2 for the initial gas concentration of 15 ppm NO. When desorbed at 353 K, NO concentration in the desorbed gas is about five times higher than that of the initial gas. It is concluded that the temperature swing adsorption process is quite appropriate for enrichment of low level NO. Although CO2 has no adverse effect on the adsorption characteristics, water vapor exerts considerable deleterious effect. Thus it is required to remove water vapor before processing.