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Types of Radon Gas Testing

The following information provides details about radon testing methods, including the advantages and disadvantages of each one. This information is intended to guide the user in making an informed selection of a measurement method.

Short-term Tests: Activated Carbon Adsorption (AC) & Charcoal Liquid Scintillation (LS)

Both of these methods absorb radon gas on activated charcoal but different equipment is used for analysis. The detectors for these methods consist of various configured containers filled with a measured amount of activated charcoal. The container is perforated or screened and has a filter to keep out radon decay products. All charcoal adsorbers are stored in air-tight containers before and after sampling.

Charcoal adsorbers are installed from two to seven days. At the end of testing, the adsorber is resealed and returned to the vendor for processing and evaluation.


  • Low cost for services; costs may range from $10 to $25 for each detector.
  • Practical for screening purposes over a short time period.


  • Some charcoal adsorbers are more sensitive than others to temperature and humidity.
  • Limited to short term testing.

Long-term Tests: Alpha-Track Detection (AT)

The detector is a small sheet of special plastic material enclosed in a container with a filter-covered opening. The radon gas that enters the container decays, emitting alpha particles. The particles strike the plastic sheet, leaving tracks that can be chemically enhanced and counted using a microscope or an automated counting system.

The detectors are installed according to instructions supplied by the vendor. They are left for periods from one to three months for screening and from three to twelve months for long-term evaluations. At the end of the desired testing period, they are returned to the vendor for processing and evaluation.


  • Relatively low-cost services ranging from $15 to $30 for each detector.
  • Can measure the long-term average concentrations over a twelve-month period.


  • Relatively long measurement period necessary; three months is the recommended minimum for most detectors.

Professional Testing: Continuous Radon Monitoring (CR)

There are three types of CR monitors used for radon measurements, usually by radon measurment professionals. The test types are: 1) Scintillation, 2) Ionization Chamber, and 3) Solid-State Detection. This type of radon monitoring follows the ambient radon levels within a short time lag due to the inherent delay of the radon decay products.


  • Follows the variations in radon levels.
  • Provides radon data on location.
  • Has the highest accuracy and precision over short measurement periods.


  • High cost for service requiring a professional to perform the measurement.
  • Limited primarily to short-term testing.