The electric field is associated with electric charge and exerts forces on another electric charge.

The magnetic field is the result of the physical movement of an electric charge (usually existing in the form of electric current) and it also exerts physical forces on electric charges, but only when such charges are in motion.

Static (not changing in time) or time-varying magnetic and electric fields exist together and are marked as electromagnetic field (EMF). Summarising, EMF is a manifestation of electrical forces associated with electric charges or currents.

The high frequency EMF is also called electromagnetic radiation (EMR).

All electrical appliances are sources of EMF. Their usage in the work environment results in a significant population of highly or permanently exposed workers. The entire general public is also exposed to EMF, usually to low-level EMF.

The interaction of time-varying EMF with electro conductive object (including human body) results in a flow of electric current, formation of electric dipoles and the reorientation of electric dipoles already present in the object (e.g. body tissues). Because of possible adverse effects from such EMF interactions with a human body or safety hazards caused by the results of interaction in the other exposed objects – EMF and electromagnetic hazards (EM-hazards) caused by EMF influence need control and limitation in the environment.

Fig. 1 The distribution of electric field emited by an electric appliance used near the human body