To protect people, international organizations have stipulated basic limits. In the low-frequency range, the current density (J in mA/m²) is used, and in the RF range the specific absorption rate (SAR in W/kg).

Measuring these basic limits is very costly and thus impractical. Usually, we measure quantities derived from the basic limits for the electric and magnetic field strengths.

The field strengths recommended by the ICNIRP (International Commission on Non-Ionizing Radiation Protection) are internationally recognized and are used in many countries as the basis for national norms and laws.