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Radon Decay Products

Radon Decay Product Measurement

The device that measures radon decay products or progeny concentration is called an Electret Passive Integrating Progeny Sampling Unit (E-RPISU®  ).The E-RPISU® is basically composed of an air sampling pump, a flow meter and an electret ion chamber with an appropriate filter holder and an electret.

Key Benefits

  • Measures Radon and Radon Decay Products simultaneously.
  • Ideal for short-term testing.
  • Provides duplicate radon decay product measurement results for QA/QC.
  • Tamper-resistant features.
  • Save costs by using standard Rad-Elec reader.
  • NEHA-NRPP approved (Device code: 8228)
  • Generate reports online for immediate results and lightning fast transmission of reports to customers.
  • Can estimate unattached fraction for even more in-depth investigations
  • Great for measuring beneficial effect of air filtration equipment.


 erpisu (222 x 394).jpgHow it works:

An air-sampling pump (0.5 to 2 liters per minute) is used to collect the radon decay products for a known sampling time on a 3.5 cm2 filter sampler mounted on the side of an electret ion chamber. The flow rate can be adjusted to the recommended rate of 0.5 to 1 liters per minute. And sampling duration 1 to 7 days.


Please see the schematic for the views of the monitoring head. The filter paper is mounted such that the progeny collected emit their radiation into the interior of the chamber. The alpha radiation emitted by the progeny collected on the filter ionizes air in the electret ion chamber. The ions are continuously collected by the electret, providing integrated alpha activity collected on the filter paper. The standard electrets and the readers used in E-PERM® System are usable with this unit. The initial and final readings of the electret, the flow rates and the duration sampling (as recorded by the time totalizer) is used in a software to calculate progeny concentration in WL units. Software is provided for data analysis.


These monitors have sufficient sensitivity to provide results with better than 10% precision at 0.01 WL for a 2 day measurement when used with LT electrets. These provide better than 10 % precision at 0.001 WL, when used with ST Electrets.


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