I cannot stress the importance of the following information! Radon testing is the only way to know whether or not your Maryland home has a problem. Do not listen to people who tell you otherwise.

Many times neighbors or real-estate agents make claims such as, “I know this neighborhood and there’s no radon.”, or “My neighbor down the street didn’t have it, so I don’t either.”, or even “I have a new home. that gas is only in older structures.”. The list goes on and on.

In 1997, I encountered a classic example of the dangers of not testing. I was called to test a home Carroll County, Maryland. The homeowner had been there for five years. The family was quite large (five children) and the lack of bedroom space required that three of the children sleep in the basement.

After inspecting the house, I was told by the homeowner that when he purchased the home his realtor had assured him that the house was gas-free. Fortunately for the homeowner, he had taken it upon himself to have his home tested. He was quite confident that the house would have no problem. You can imagine his shock when he found out that the radon level in the basement was 300 pCi/L!

The point I’m trying to make is, whether you believe in the radon issue or not, EVERY HOME HAS THE POTENTIAL OF HAVING A PROBLEM! If you do not test, you will never know!

Finally, consider the possibility you’ve decided to sell your Maryland home. Having it tested will allow you to more accurately adjust your asking price. Radon testing will also save you the time and expense of correcting a radon problem should a potential buyer decide to do his or her own test just prior to settlement. Finally, a house that is advertised as tested and mitigated for radon will be more attractive to buyers and will probably sell faster.


There are two types of testing. Short Term Testing and Long Term Testing.

This is the most common type of testing done in the industry today. This type of testing is usually 2-7days of exposure to a testing device. It is primarily used in real-estate transactions. Since most radon addendums that are attached to real-estate contracts put time limits on buyers to find out if a problem exists, this type of testing is the only way to meet the time line.

The testing devices used in this type of testing are Charcoal Canisters, E-perms, or Continuous Monitor Devices. There are pros and cons to each type of short term test which are covered later.

Homeowners that are concerned with the overall annual radon level usually use this type of testing. In some cases short term testing may show levels of 3.9 pCi/L or 4.6pCi/L. In this situation the homeowner may do a long term test which might show annual levels of only 2.6 pCi/L which would not require a radon mitigation system. This type of testing is ideal for radon levels that are close to the E.P.A. action level of 4 pCi/L. This type of testing device is called an Alpha-track.

NOTE: If you are involved in a real estate transaction this test is not an option for you because of the time constraints.


What follows in an overview of testing devices, a brief description of their functions, and pro’s and con’s of each devise. Your testing device might look different or have directions contrary to this information. Always follow the directions in the testing kit or those given by a licensed radon testing contractor.

Charcoal canisters: This device uses activated charcoal in a canister to absorb the radon-laden air in the testing area. Exposure time is 2-7 days. When testing is completed the charcoal canister needs to be analyzed as soon as possible by the laboratory who sold the device. Radon levels are determined by the gamma emissions coming from the canister.


  • low cost testing
  • convenience
  • simplicity of use
  • easy to mail


  • measurements biased to the last 12-24 hrs
  • sensitivity to temperature and humidity
  • sensitivity to air flow extremes

E-PERM: This testing device uses an electrostatically charged material that looks like a Ritz cracker inside a plastic chamber. When radon enters the chamber the voltage inside the chamber drops. Therefore, the amount of voltage reduction is directly related to the radon concentration and the length of exposure.


  • low cost testing
  • measurement analysis can be done on site with a special electric reader
  • devise can be used multiple times until voltage is depleted


  • trained tester needed to use devise
  • special equipment needed for results
  • device sensitive to background radiation

Continuous Radon Monitors: This testing device uses electricity. It is a complex unit that measures the radon in a tube called a scintillation cell/photo multiplier. As the radon gas enters this chamber the devise counts the breakdown of the gas. When radon decays it goes from a gas to a solid, when this happens, a mini explosion occurs. This device counts the flashes of light the decaying process produces. The number of flashes of light corresponds to a specific quantity of radon.


  • very accurate testing
  • results not bias to last 12-24 hrs
  • less sensitive to temperature, humidity, air flow
  • this type of testing ideal when time is of the essence


  • more expensive than canister testing
  • need specific knowledge to run devise and interpret results

Alpha Track Detectors: The only true long term testing device (90 day to one year), this detector works very well and is not as delicate as other tests. The concept is very simple. Inside of a plastic casing is a special film. As the radon gas decays from a gas to a solid, the solid produced strikes the film in the casing leaving a mark on the film that looks like a crater. After the device has been exposed for 90 day to a year it is sent back to the lab. The technician counts the craters. The number of craters multiplied by the length of the test corresponds to a specific radon level.


  • low cost
  • simple to use
  • true integration ( not biased toward most recent exposure)


  • need skilled technician to interpret results
  • sampling conditions during the measurement period which could affect results may be unknown