Radiofrequency field surveys in hospitals

The authors surveyed levels of radiofrequency (RF) fields in the frequency range 0.1-1,000 MHz in four hospitals in the Philadelphia area, to obtain background information related to the possible interference of radiofrequency fields with medical equipment. Two large center-city hospitals, a regional county hospital, and two suburban hospitals were surveyed. Measurements were made at six to 12 sites in each hospital, in each of the three frequency bands. More limited additional measurements were conducted in a fifth hospital as well. Sites were selected to include areas where strong RF signals from transmitting antennas might be expected to be present (e.g., locations close to windows in upper stories of buildings near paging antennas) as well as other representative sites in the hospital. The median RF field strengths were quite low (0.1-0.5 V/m), but at specific locations the RF signals from broadcast sources exceeded 1 V/m. Much stronger fields were recorded close to electrosurgical units and hand-held transmitters (cellular telephones and UHF transceivers).