An on-site apparatus that produces cryogenic temperatures is used to remove, by condensation, all pollutants in the air so that an ultra clean air supply is obtained for human consumption in the interior of living enclosures, such as automobiles, homes, offices, hospitals etc. In accordance with one embodiment of the invention, it can recycle the air in the enclosure, i.e. resupply the oxygen consumed by the human being and remove the carbon dioxide produced by respiration. The cryogenic temperatures are produced by a closed-cycle operated refrigeration system consisting of a compressor, a Joule-Thompson valve (JTV), multi-stage heat exchangers and expanders. Cold traps (filters) of different cryogenic temperatures are built into the system to condense pollutants of different condensation temperatures. The condensed pollutants can be disposed of by periodical defrost and purge of the system.