The statistical foundation that underlies the development of detection limits in ASTM D6620-19, Standard Practice for Asbestos Detection Limit Based on Counts, is described. The roles of, and relationships among, laboratory background asbestos measurement distributions, decision values for classifying a measurement as below detection, and probabilities of classification errors are defined and analyzed. The application of detection limits for asbestos defined by ASTM D6620 for guiding study designs is presented using two examples: (1) compliance with the Occupational Safety and Health Administration permissible exposure limit; and (2) limiting cancer risk associated with asbestos exposure. In addition, the detection limit as a study design parameter is contrasted with an approach to study design using confidence intervals with a specified limit on estimation error.