A deodorant filter was made by treating porous metallic iron with an L-ascorbic acid aqueous solution, depositing the iron ascorbate on it. The ammonia adsorption capacity of the deodorant filter was studied with repetitive runs of adsorption tests. The results show that the ammonia adsorption capacity of the iron ascorbate is nealy equal to conventional granular activated carbon at the beginning, but unlike the letter, the iron ascorbate perfectly recovers the capacity via reversible desorption. ESR and Mossbauer spectroscopy reveal that ammonia goes into the inner coordination sphere of Fe (II) and Fe (III), capable of reversible adsorption and desorption, and that the reactivity of iron is attributable to the formation of the ascorbate complex, which is formed in the specific manufacturing process of the deodorant filter.