Radon is one of the noble gases, which are chemically inert and do not make any reactants under normal conditions. In this experiment we demonstrated an enigmatic reaction between radon and fluorine when a corona discharge is used as a promoter. Distinctive changes in radon concentrations were caused by the discharge and a trap efficiency of >99.5% was estimated. The mass balance between the trapped and the released radon was found to be reasonable. This indicates the existence of chemical reactions with radon. This trap phenomenon has application as a technique for reducing radon concentration in radon-contaminated air. It is possible that this technique will be applicable to other noble gases.