The Effects of Distance and Warming Temperature on Intensity of Extremely Low Frequency Electromagnetic Field from Forced-Air Warming System

Purpose. Electronic devices, increasingly used in operating rooms, heavily depend on mains electricity. This may significantly increase occupational exposure to extremely low frequency electromagnetic field. As a possible carcinogen as per International Agency for Research on Cancer, Swedish Confederation of Professional Employee recommended it should be below 2 mG. Forced air warming system is used to prevent hypothermia. This study was to investigate the effect of distance and warming temperature on extremely low frequency electromagnetic field intensity from Bair-Hugger™ Warming Unit, in order to find the minimum safe distance from the device. Materials and methods. The forced-air warming unit was hung on the side of an operating table in an empty operating room, with all other electronic devices turned off. With three different warming temperatures, electromagnetic field was measured at 15, 30, and 45 cm from the anterior surface of the device. Data was collected at a sampling time of 0.5 times per second for 10 minutes. Kruskal-Wallis one-way analysis was used. Results. Increasing warming temperature and reducing the distance from the device resulted in a significant increase in electromagnetic field intensity (p <0.05). At 45 cm in particular, low and medium warming temperatures showed significantly lower intensity compared to high temperature (p<0.05). Exposure below 2.0 mG was achieved only when it was at 45 cm regardless of temperature. Conclusions. Health workers should be aware of occupational exposure to extremely low frequency electromagnetic field and avoid as much as possible. It is suggested to stay at least 45 cm away from 3M Bair Hugger™ Warming Unit.