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The effectiveness of a shield in reducing operator exposure to radiofrequency radiation from a dielectric heater.

Murray-WE; Conover-DL; Edwards-RM; Werren-DM; Cox-C; Smith-JM
Appl Occup Environ Hyg 1992 Sep; 7(9):586-592
The effectiveness of a shield for reducing exposures to radiofrequency (RF) radiation from dielectric heaters used in water bed mattress manufacturing was evaluated. The shield, a cabinet like device containing two sliding interlocking doors, was placed between the base plate and press yoke of the dielectric heater used to seal water bed mattresses. The shield contained a 1.27 meter by 12.7 centimeter slot in the front to allow the material to be sealed to be positioned properly and the excess folded out of the way. After this was done the interlocking doors were locked and the RF power was activated. The shielding device was tested at a water bed mattress manufacturer located near Cincinnati, Ohio. Thirteen RF heaters which were usually operated by 15 to 25 employees were used at the factory. Mean squared electric and magnetic field strengths and the foot current were measured before and after the shields were installed. Before the shields were installed, the RF electric and magnetic field strengths ranged from 80,000 to 770,000 volts per meter squared ((V/m)2) and 0.53 to 4.0 amperes per meter squared ((A/m)2). The foot currents varied from 33.4 to 94.0 milliamperes (mA). After installation of the shields, the RF electric and magnetic field strengths ranged from 700 to 6,600(V/m)2 and 0.038 to decreases represented average reduction factors of 213 for RF electric field exposures, 10.8 for RF magnetic field exposures, and 4.3 for foot current exposures. The authors conclude that the shield has achieved significant reductions in exposure to RF electric fields generated by dielectric heaters at the facility. Lesser reductions to RF magnetic field and foot current exposures have also been obtained.
NIOSH-Author; Electromagnetic-radiation; Occupational-exposure; Magnetic-fields; Electrical-fields; Radiation-shielding; Equipment-design; Occupational-health
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Applied Occupational and Environmental Hygiene