ERPISU Development
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Although some radon professionals may view the E-RPISU as a new and unproven device, it has actually been with us for many years. However, it's more historic configurations were expensive and difficult to use. During the mid-1990s researchers at PGL began experiencing more and more situations where the direct measurement of radon decay products in addition to radon would provide a clearer indication of exposure. At that time, we approached Dr. Paul Kotrappa of Rad-Elec, who had developed a single-head radon decay product monitor in the early 1990s to see if the device could be packaged with a second radon decay product measurement device (for duplicates) as well as a collocated radon monitor to provide the desired complete reporting method, all of which used the simple and proven electret technology. What was also needed was a simple method for calculating results for this involved method. What resulted was the current configuration of the Mark-2 E-RPISU that is now available through PGL or Rad-Elec as partners. The following description of the development of the historic Mark-2 E-RPISU was provided by Dr. Paul Kotrappa.
Definition and Development of the Rad Elec Mark-2 E-RPISU Dr. Paul Kotrappa President, Rad-Elec Corporation Definitions: RP - Radon progeny integrating sampling unit (RPISU)
For this method, a low-flow air pump pulls air continuously through a filter. Depending upon the detector used, the radiation emitted by the decay products trapped on the filter is registered on thermo-luminiscent dosimeters (TLD), an alpha track detector or an electret. The devices use requires access to household electrical supply, but does not require skilled operator. Deployment simply requires turning the device on at the start of the sampling period and off at the end. After sampling the detector assembly is shipped to a laboratory where an analysis is made using a standard E-PERM® reader.. Development: Development of E-PERM® radon monitor (1989-1990) and USEPA acceptance of the device for measuring radon in homes, established the electret as a viable sensor of ionization caused by the alpha radiation emitted by radon and radon daughter products. Radon progeny integrating sampling unit (RPISU) is generic name given to instruments which collect radon progeny on a filter paper and register the alpha radiation from the deposited progeny during the entire period of collection. Different sensors can be used. E-PRPISU uses the electrets as sensors. The concept of using electret as a sensor for measuring the radon progeny collected on a filter was researched under a research contract with Department of Energy (DOE/ID/12584-43, UNC/GJ-TMC-5, 1989). Final design was evolved and the device was submitted for listing under the category RP. The performance was evaluated as a new device. Evaluation included different progeny concentrations, at different humidities and at different condensation nuclei counts. The reported concluded that "the instrument performance was satisfactory and a measurement was never more than 12% off from the chamber value". USEPA listed this device as "Rad Elec E-RPISU Mark-2 Monitor" BO094 and the listing continued by other certifying agencies. EPA/NEHA Accepted Measurement Methods (page F-10 and A-4, EPA 402-R-95-013 1995)
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