Hand & Shoe Monitors are instruments for surface contamination measurement. In nuclear facilities, Hand & Shoe Monitors are installed usually at the exit from the controlled areas and workers are usually required to measure, whether their hands and shoes are contaminated or not. Generally, surface contamination means that radioactive material has been deposited on surfaces. It may be loosely deposited, much like ordinary dust, or it may be quite firmly fixed by chemical reaction. This distinction is important, and we classify surface contamination on the basis of how easily it can be removed.
These monitors may utilize gas-flow proportional counters with a large area, they are used in various locations in the station to detect beta gamma contamination on hands, shoes and clothing. In order to detect beta radiation, these large area detectors have thin Mylar windows to allow low-energy beta particles to enter the detector. For example, they can easily detect the low energy beta particles emitted by carbon-14 (Emax = 156 keV). When instruments are operated in the proportional region, the voltage must be kept constant. If a voltage remains constant the gas amplification factor also does not change. Proportional counter detection instruments are very sensitive to low levels of radiation. By proper functional arrangements, modifications, and biasing, the proportional counter can be used to detect alpha, beta, gamma radiation. The electronics sorts the alpha, the beta-gamma pulses. This feature may be used in alpha, beta-gamma Hand & Shoe Monitors, Full-Body Monitors, some alpha Contamination Monitors. Although such detectors are very sensitive, their drawback is that the windows are punctured quite easily by misuse. The detector is then dead until its window is repaired.