10.5.4 Direct RF Exposure Hazards

The most obvious hazards are the electromagnetic fields produced directly by transmitting equipment.

Depending on frequency and exposure conditions, direct RF exposure may cause electrostimulation at lower RF frequencies or tissue heating over much of the RF range if the applicable basic restrictions are exceeded. Reference levels provide practical quantities for assessing compliance. The potential hazard also depends on source power, antenna characteristics, beam direction, operating pattern, and a person's location and activity.

Hazard identification should consider normal maximum operating conditions and reasonably foreseeable abnormal or maintenance conditions, including work performed with sources energized.

10.5.5 Indirect And Secondary RF Hazards

Not all RF hazards arise directly from antennas.

Strong RF fields may induce currents in nearby conductive objects, creating indirect contact-current, spark, shock, or RF-burn hazards. Because these hazards depend strongly on behavior and on the configuration of the source, object, and contact, ICNIRP and RPS S-1 do not prescribe contact-current restrictions; they provide guidance so that the hazards can be identified and controlled. Metallic fences, guy wires, ladders, cranes, handrails, pipelines, cable trays, and other conductive structures should therefore be included in the assessment.

Reflections and reradiation from buildings, metallic structures, vehicles, or other objects may also produce localized field maxima or alter the exposure pattern. These effects can be less obvious than the primary source and may require site measurement or more detailed modeling.