The electromagnetic field which electrical devices spread out can be dangerous for human. The special attention is paid to a magnetic component of an electromagnetic field of industrial frequency. Electric reactors with the air core concern to the electromagnetic devices which create the strong electromagnetic field. In order to reduce the influence of magnetic field to the persons' organism, measures should be taken on its reduction: shielding of workplaces; use of shielding waistcoats: exception of long exposure in places with the raised level of the industrial frequency magnetic field. Recently many new materials with unique properties were developed. Therefore, shielding is one of the most perspective approaches to the solution of the problem to decrease in inadmissible levels of electromagnetic fields.