The possible spread of contamination to clean areas was controlled by requiring personnel who entered a contaminated area to exit through a check point where they could be monitored and decontaminated as necessary. Most scientific project or other personnel whose activities required entry into highly radioactive areas were issued anti~contamination clothing (including coveralls, booties, and gloves) that could be easily removed, if needed, at the check station decontamination point. It should be emphasized that such clothing did not provide any more protection against external radiation (alpha, beta, or gamma) than did ordinary clothing or military fatigues. This disposable clothing was provided simply as a convenience for contamination control and laundry purposes. Ordinary clothing and fatigues that could not be decontaminated also had to be replaced at the check station decontamination point. 5.2.2 Use of Radiation Detection and Measurement Instruments. Monitors used several types of radiation survey instruments. The ‘ majority were gas-filled detectors, specifically ionization chamber, GeigerMueller counter, and gas-flow proportional counters. These detectors relate the intensity of the incident radiation to the effects of ionization produced by the radiation in a gas-filled "sensitive volume." Some of the other instruments took advantage of the fact that certain materials emit light when struck by radiation. These instruments, called scintillation detectors, simply relate the amount of light produced in the detection medium to the intensity of the incident radiation. Both gas-filled and scintillation detectors were used, depending upon the basic design of the instrument, to detect and measure alpha, beta, and/or gamma radiation. The survey instruments mentioned above portray the radiation intensity in terms of rate (e.g., milliroentgens or roentgens per hour or counts per minute). In some cases, test participants were issued pocket dosimeters that provided information on cumulative exposure. These dosimeters, about the size and shape of a writing pen, consisted of a small ionization chamber coupled to a miniature electroscope. One type of pocket dosimeter (self-reading) included an optical system that allowed the wearer to determine his cumulative exposure while in the field. Other types required a separate charger-reader. 145