Shielding device for attenuating electromagnetic fields in buildings, comprising:a) an AC power sourceb) at least two frequency attenuation units (1), each comprising a conductor (2), being coaxially arranged in a glass or metal tube (3), wherein said conductor (2) is wrapped in an insulating material (4), and said conductor (2) is electrically connected to said power source andc) at least one metal plate (5), provided between two of said frequency units (1).
