An evaluation of safe practices to restrict exposure to electric and magnetic fields from therapeutic and surgical diathermy equipment.

Stray electric and magnetic fields have been measured near to therapeutic and surgical diathermy equipment for many different treatments. The highest field strengths are associated with continuous wave (cw) 27 MHz therapeutic diathermy equipment for which fields above national reference levels extend for 1 m from the electrodes and cables. The extent of the fields does not vary substantially with the type of treatment being performed. Recommendations that operators remain 1.0 m from cw therapeutic diathermy equipment, 0.5-0.8 m from pulsed treatments with capacitive electrodes and 0.2 m from pulsed inductive applicators can be applied to restrict exposure for any treatment with each type of unit. In a proposed European Community (EC) directive, action levels similar in magnitude to the reference levels are used to trigger requirements for assessments of hazard, measures to reduce exposure and personnel training. Assessments and appropriate recommendations of measures to reduce exposure can be linked to the type of equipment. Fields associated with electrosurgical units operating at frequencies of 0.3-0.5 MHz only approached reference levels within 20-30 cm of the cables, and because of the relatively short durations of the emissions, precautions were considered unnecessary with the units tested.