How do I Choose the Best Radon Gas Detector?

Kay Blynn

Radon gas is an odorless, tasteless and colorless radioactive gas that occurs naturally with the decay of radium. Radium is a naturally occurring chemical in most soil and rocks. Typically, radon gas is released into the atmosphere is such small amounts that it is not considered harmful. Recent studies indicate that radon gas can accumulate in confined spaces and can cause potential health hazards, including lung cancer. In recent years, several types of radon detectors have become available to both home owners and builders. They include passive, short-term detectors, and active, long-term detectors. Considerations for choosing the right one include whether or not a source of electricity is available, whether the detector is spot checking or will be in continuous use and what size area needs to be checked.

People who risk chronic exposure to radon through work or in other locations should take safety precautions.
People who risk chronic exposure to radon through work or in other locations should take safety precautions.

A passive, short-term radon gas detector does not require electricity. It typically contains a charcoal canister that is exposed to the air in a home for a short period. The test period for passive detectors vary by manufacturer. Some radon gas detector kits require a three- to seven-day test period, while others are designed to test for 90 days or one year. After the test period is over, the canister is shipped to a company which can safely test the sample for hazardous radon gas levels. These companies typically send a letter to the homeowner with the test results.

Difficulty breathing is a symptom of radon poisoning.
Difficulty breathing is a symptom of radon poisoning.

An active radon gas detector is powered by electricity and can monitor radon gas levels twenty-four hours a day. Most models have a digital read out and sound an alarm when radon gas levels become hazardous. Radon is measured in units called picocuries, which measure the rate of radioactive decay — 1 picocurie is equal to the decay of two radioactive atoms per minute, and they're typically measured in picocuries per liter (pCi/L). According to the Environmental Protection Agency (EPA) in the United States, long-term exposure to radon gas levels above 4 pCi/l, is considered a potential health hazard.

Carefully following the directions when using a passive or active radon gas detector is very important. The key to a successful radon gas test is placing the detectors properly. Radon gas is a heavy gas that tends to accumulate in low-lying areas, such as basements, cellars and first floors that come into direct contact with the soil. A radon test kit should be placed at the lowest level of the home possible, and high humidity or drafts can interfere with an accurate radon gas reading.

Large-scale, multiple-reading radon test kits are available to contractors and builders of new construction. These tests can also detect radon levels in large, existing buildings. Land can also be tested for radon gas emissions prior to starting new construction. These tests are typically called open land test kits and generally operate in the same manner as the home detectors.

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Discussion Comments


The answer above says that radon is a heavy gas that tends to accumulate in low-lying areas. While radon is the heaviest gas, this has no significant effect on where it accumulates. It will quite easily travel to the top floor of high-rises.

The reason it is most often present at higher levels in basements, crawl spaces, cellars, etc. is simply that these areas are closest to the source of radon, i.e., the soil.


Radon gas has radioactive properties and can contribute to acute respiratory health risks, such as lung cancer (one in 20 will develop lung cancer due to elevated exposure1). This is especially true if you are a smoker or are exposed to second hand smoke on a consistent basis.


You can find more information about what radon is, how radon occurs, why it is harmful, not least how you can make radon measurements in your own home.

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