Evaluation of Protective Hoods in Strong RF Electromagnetic Fields

Protective garments made with conductive fibers are used to reduce human exposure to both extremely low frequency (ELF) and radio-frequency (RF) electromagnetic fields. The former are usually associated with high-voltage systems and the latter with communication systems. The fundamental difference between RF and ELF protective garments is the head covering; the former has a conductive screen in front of the face while the latter does not. Near high-voltage transmission lines on which communication antennas are mounted, both ELF and RF electromagnetic fields exist. High-voltage transmission line workers may use a high-voltage protective suit in this environment. There is reason to believe, however, that the partially open head covering of a high-voltage suit may act as a resonant cavity when exposed to incident RF energy. Thus, it is possible that the RF field in the workers head may actually be enhanced by wearing the suit. A series of experiments was conducted to determine whether this phenomenon occurs. It was shown that there appears to be a modest resonance within the partially open head covering in the vicinity of 800-900 MHz that causes the RF electromagnetic fields in the head to exceed those in the head without a conductive suit