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Environmental Consultations

Radon Long-Term Measurements (91 - 365 days)


According to the EPA, a long-term radon test is the best way to determine your exposure to radon during different seasons and living conditions in your home. Closed house conditions are not necessary during long-term radon tests. EPA recommends using 2 canisters per 1,200 square foot dwelling.

For Long-Term Radon-222 Measurements with exposure times between 91 days and 12 months, Potomac Homes deploys either:

  • E-PERM Long-Term Electret Radon Monitors*, which are the most accurate professional true integrating detectors that can measure fluctuating radon concentration regardless of extreme temperatures or humidity.

    At the end of the test, Potomac Homes measures immediately and within the premises the Radon-222 concentrations and gives its client a comprehensive computerized report.


  • AT - Alpha Track Detectors (filtered), with an improved diffusion-based track detector filtering out dust and radon progeny through a structural filter that is an integral part of the housing, resulting in increased sturdiness.

    These EPA certified detectors are designed for:

    • minimizing electrical charge effects from the positively charged radon progeny generated inside the detector.

    • maximizing sensitivity and creating a more uniform track distribution for better counting statistics.

    Exposure of alpha track detectors is usually 91 days to 12 months, but because they are true integrating devices, alpha track detectors may be exposed for shorter lengths of time when they are measuring higher radon concentrations.

    At the end of the test the container is sealed and returned to a NEHA accredited laboratory for reading.

    * Detectors using this technology were found superior to chemically etched alpha track radon detectors in an article comparing radon detection methods by John Matuszek of the New York State Department of Health (J.M. Matuszek, et al., "Standardization of Radon Measurements", Environmental International, December 1988).

Long-term testing should be conducted in a frequently occupied room or in a room where previous short-term has indicated a potential concern. There are no special conditions for operating the building


The EPA recommends that you fix your home when the radon level is 4 pCi/L or more and we suggest that you contact a qualified radon reduction contractor about lowering the radon level if results of the above tests are over this threshold.


Another level set by the EPA is 2.0 pCi/L ("Consider Action Level"). At this level, the EPA recommends that you consider installing radon abatement systems in your home to reduce your indoor radon levels.

[more about radon]


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Last modified: 03/28/2017

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