Most electronic equipment is, in some manner, affected by electromagnetic radiation. This radiation is frequently generated by such sources as cell phones, two way pagers, and small handheld radio transceivers that are used by operating, maintenance and security personnel, fixed station radio and television transmitters, vehicle radio transmitters, and various industrial electromagnetic sources.

In addition to electromagnetic energy deliberately generated, there is also spurious radiation caused by devices such as welders, thyristors, fluorescent lights, switches operating inductive loads, etc. For the most part, this interference manifests itself as conducted interference and, as such, is dealt with in other parts of this standard. Methods employed to prevent effects from radiated electromagnetic fields will normally also reduce the effects from some of the conducted emissions.

The electromagnetic environment is determined by the strength of the electromagnetic field (field strength in volts per meter). The field strength is not easily measured without sophisticated instrumentation nor is it easily calculated by classical equations and formulas because of the effect of surrounding structures or the proximity of other equipment that will distort and/or reflect the electromagnetic waves.