Abstract: A method is disclosed herein for treating the gaseous effluents emitted from a nuclear reactor, said method being adaptable for treating either gaseous effluents produced during normal reactor operations or combustible and fission product gases released as the result of a nuclear reactor system failure. The treatment comprises sequential direction of the gaseous mixture through a multiplicity of adsorbent beds, each of said beds being preferentially adsorptive towards at least one component of said gaseous mixture, whereby to effect the desired separation by substantially either thermal-swing, cryogenic, or rapid cycle adsorption techniques.