Abstract
In 1990, the American National Standards Institute (ANSI) published a standard on “Performance Specifications for Health Physics Instrumentation—Occupational Airborne Radioactivity Monitoring Instrumentation.” This standard specifies performance criteria and testing procedures for instruments and instrument systems designed to continuously sample and quantify concentrations of radioactivity in ambient air in the workplace. This article discusses specific criteria in the ANSI standard regarding instrument performance and design and the results from testing different air monitors using procedures based on the criteria in the standard. Criteria in the standard are divided into the following categories: general, electronic, radiation response, interfering responses, environmental, and air circuit. Testing results from each of these categories are given. Results from tests of response time, coefficient of variation, beta-energy dependence, and environmental conditions (i.e., temperature, humidity, ambient pressure) indicate that the response of some instruments can vary substantially under different exposure conditions. Systems tested against the criteria for stability, alarm threshold drift, and air flow-rate accuracy criteria performed well. Results suggest that deposition of large particles is a problem in the sampling inlets of some continuous air monitors. In this article, both performance criteria stated in ANSI N42.17B and specific testing results are discussed. The test results reveal that certain systems may exhibit large temperature, humidity, or ambient pressure effects; large variability in readings; very slow response times; large beta-energy dependence; a saturation problem in high-exposure conditions; or large loss of particles in the sampling inlet. In many cases the effect on the instrument performance is such that the level of exposure to personnel is underestimated or the ability of the system to alarm at the proper level is impaired. Other air monitoring systems perform adequately when compared to the requirements in the standard. Kenoyer, J.L.; Hickey, E.E.; Swinth, K.L.: ANSI N42.17B-1989: Performance Testing of Workplace Air Monitors Used To Measure Occupational Airborne Radioactivity. Appl. Occup. Environ. Hyg. 8(4):317-323; 1993.