A simple and rapid method of characterization of carbon sieves used as adsorbents in pressure swing adsorption technology for the separation of nitrogen from air and hydrogen from process gases has been worked out under a dynamic conditon of molecular probe chromatography. The carbon sieves, CMSN2 and CMSH2, reproducible products of Bergwerksverband GmbH, Esssen, Germany, used in the recovery of nitrogen from air and hydrogen from process gases, respectively, by pressure swing adsorption have been suggested as the standards for the comparative evaluation of such sieves. The method has the advantage that the measurement can be carrried out with a simple gas chromatograph without using an expensive data acquisition and processing unit. The method has the potential to be used with other carbon sieves either in equilibrium or diffusion-controlled gas separations. It is especially suitable for monitoring the products during the development stage.