[en] One of the remedial action measurements needs is the estimation of average indoor radon-daughter concentration (RDC). One method for accomplishing such estimations is the Electric Radon Progeny Integrating Sampling Unit (ERPISU) method. Electronic RPISUs differ from standard RPISUs in that an Electronic RPISU measures radon-daughter concentrations using a solid-state alpha detector, rather than the thermoluminescent dosimeter employed by a standard RPISU. This procedure manual describes hoe to set up and operate a system for obtaining ERPISU measurements, and how to derive annual average RDC estimates from those measurements as well as RDC estimates for comparsion against selected standards. This manual contains both procedures specific to the Elberine WLM-1A Working Level Monitor and general guidelines applicable to any type of Electronic RPISU that may be approved by DOE. Necessary equipment items include samplers, readout units or computer interfaces, filters, radioactive alpha standard, and an airflow measuring device. The annula average radon-daughter concentration is estimated as the mean of six such measurements, each approximately one week in duration and spaced approximately two months apart. Criteria for making fewer than six measurements, including the abbreviated RPISU method, and for handling missed or invalid measurements are also presented. 9 refs., 4 figs., 2 tabs