The Effectiveness of a Shield in Reducing Operator Exposure to Radiofrequency Radiation from a Dielectric Heater

Abstract

Abstract The objective of this study was to design and install a shield on a radiofrequency (RF) dielectric heater used in the water bed industry and to determine its effectiveness in reducing worker exposures. In work sites where industrial dielectric heating is utilized, occupational RF radiation exposures frequently exceed occupational exposure limits. A water bed manufacturer that used dielectric heaters in its production operations agreed to participate in this developmental study. The mean-squared (ms) RF electric (E 2) and magnetic (H 2) field strengths, the root-mean-squared (rms) RF-induced foot current and the heater frequency were measured for each unit. A heater utilizing a common sealing process and producing high worker exposures was selected for this study. The water bed mattress is a large, bulky product and can not be contained inside the shield. Thus, the shield required a slot or opening to allow passage of the material between the applicator plates for sealing while minimizing the leakage of RF radiation. An RF engineering firm designed, fabricated, and installed the shield. Operator exposures were measured before and after installing the shield to determine the shield's effectiveness in reducing RF exposures. Using these data, average exposure reduction factors were calculated: ms E-field strength (E 2)—213 times; ms H-field strength (H 2)—10.8 times; rms foot current—4.3 times. Thus, the shield was effective in reducing the operators' RF exposure from the heater.