Airborne radioactivity may be measured by three main methods: sampling techniques followed by suitable monitoring, sampling techniques concurrent with suitable monitoring, or by directly measuring the radioactivity from a known volume of air. This paper discusses the interpretation of air sampling and monitoring data obtained from the first two techniques, including the effect of half life on sample radioactivity. Subjects covered are: derivation of air sampling equations, evaluation of data from fixed collecting medium continuous air monitors, evaluation of data from moving collecting medium continuous air monitors, with immediate counting or with post collection counting, evaluation of data for the above air monitoring instruments when (a) the half life is short compared to the sampling interval of concern, (b) the half life is long compared to the sampling interval of concern and (c) the half life is similar to the sampling interval of concern. The effect of changes in concentration as a function of time is also discussed. Examples are given for each condition.
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