Nebraska Radon Program
Testing Methods

Because of its nature, indoor radon concentrations can be determined using a variety of testing methods.  Several of the commonly available testing methods are explained in the following paragraphs:

Activated charcoal detectors (AC):  Charcoal detectors, manufactured in various forms, use activated carbon, which has a strong affinity for gases and vapors, to adsorb radon gas.  These short-term tests have exposure times between two and seven days, depending on the manufacturer.  After exposure, they are resealed and returned to a laboratory for analysis.  Although they are seldom available in retail store, charcoal detectors range in price from $10 to $25.  Many local health districts purchase these devices for free or reduced cost distribution to the public.

Alpha track detectors (AT): Alpha track detectors, manufactured in various forms, use a thin section of plastic called a "foil" mounted inside the container.  Filter fabric is used to cover the opening that permits the room air to diffuse into the container but denies entrance to particulate matter.  Alpha particles emitted by radon and radon progeny inside the container, near the foil, strike the plastic leaving an indentation or "track".  In the lab, an etching process makes damaged regions more visible.  The tracks are then counted to determine the radon level in the room where the detector was exposed.  Alpha track detectors must be exposed in the home for a minimum of 90 days but can be left exposed for up to twelve months (a test of 100 to 120 days is recommended).  Alpha track detection devices typically cost  $20 to $30 and are available through the mail or can be ordered at most hardware stores.

Electret ion chambers (EC): Electret ion chambers consist of a small plastic container with a charged electret attached to the bottom and a filtered inlet at the top.   Negative ions formed from collisions of alpha particles with atoms in the chamber cause voltage to be discharged from the electret.  The change in the electrical voltage, measured in the lab by a voltmeter, is used to determine the radon concentration where the detector was deployed.  With an EC the results are available within a few hours after the measurement is complete.  The system can be used for either short-term or long-term measurements, depending upon electret type, and measurement costs may range from $75 to $150.

Continuous radon monitors (CR.) and continuous working level monitors (CW):     These measurement methods use electronic detectors to accumulate and store information related to average concentrations of radon gas or radon progeny.   These short-term instruments can track variations in radon concentration over time.   Most models are very precise and results may be available on-site or within a few hours after the measurement is complete.  These devices must be operated by skilled technicians and the service generally costs from $85 to $150.

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