How Long to Air Sample? Practical Considerations for Short-Term Air Sampling

Abstract

Transportable (e.g., "giraffe") air samplers can be used for both short-term "grab-sampling" situations involving a few minutes to several hours, as well as for long-term retrospective air sampling situations that typically last a week. It is the short-term coverage situation which begs the question: "how long a sampling time is adequate?" The basis for the answer (which depends mainly on the selected volumetric sampling rate and the counter sensitivity, as well as the concentration level to be measured) can be simply viewed as follows: that an adequate activity must be measureable on the air filter sample at the cessation of sampling. Equations for selection of sampling times are presented, as are example calculations for alpha counters in order to measure various target concentrations and exposures. The concepts presented here can be readily adapted to other counting systems as well as to different sampling flow rates.