Electromagnetism. These levels are provided for practical exposure assessment purposes to determine whether the basic restrictions are likely to be exceeded. Reference levels for external field strengths or power density are derived from relevant basic restrictions using measurement and/or computational techniques, and some (e.g. for contact currents) address perception and adverse indirect effects of exposure to EMF.
Following physical quantities are used: electric field strength (V/m), magnetic field strength (A/m), magnetic flux density (T), power density (W/m2), and contact current (A). In any particular exposure situation, measured or calculated values of any of these quantities can be compared with the appropriate reference level. Compliance with the reference level will ensure compliance with the relevant basic restriction.