In this paper we present a theoretical study of the plane waves in chiral media. The ability of a shielding enclosure is characterized by its shielding effectiveness. We are particularly interested by chiral devices and their importance to improve the shielding effectiveness. An analysis of the shielding effectiveness for typical materials in function with frequency has been done. The typical materials used for shielding are the copper, aluminium and steel. In order to do a comparative study between the different types of materials, the results obtained are presented. Due to chirality, there is magnetoelectric coupling. The electric and magnetic shielding effects are shown to be function of the three material parameters. We found that, at normal incidence, reflection is found to occur similar to that for the isotropic medium. The cross-polarization effects caused by the chirality will appear at oblique wave incidence.