Testing Strategies

There are two different strategies that can be employed when performing a radon test:

1. Screening Method

   • The goal in a screening test is to quickly screen the entire structure for high levels of radon, using as few tests and as little time as possible.

2. Exposure Method

   • The goal in an exposure assessment test is to determine the approximate exposure a person would have to radon in this building under normal living conditions.

Alpha Energy Laboratories’ instructions are generally designed for the Screening Method, as this is most appropriate for the typical person.

Regardless of your testing strategy, you should follow Closed House Conditions, where all exterior doors and windows are closed for at least 12 hours prior to the test and for the test duration. Closed House Conditions help to stabilize radon levels in the home for more consistent results.

Screening Method

To screen a building for radon, you want to temporarily create conditions where radon levels will be as high as possible, and you want to test in a place where radon is mostly likely to be found. This ensures that if there is radon present in the building, you will have a good chance to find it in your test. The screening method is generally the best choice for most people and is strongly recommended for initial testing.

In most buildings, radon enters from the ground through the foundation. Radon gas is heavier than air, and when possible, it prefers to gather in low spots in a building. These two factors mean that radon is typically most concentrated on the lowest floors of a building, whether that be a basement or the ground floor. Therefore, the Screening Method recommends that you place the test on the lowest floor of the home which could be inhabited by a person, whether it is finished or unfinished. This means you should test an unfinished basement, for example, if the basement could one day be renovated to become habitable. You should not test areas that will never become habitable, such as a crawlspace. 

The screening method requires the fewest number of tests to screen a home for radon. For most single-family homes, only one test is needed. If the result of this test comes back showing a low level of radon, it is very likely that the upper floors of the building also have low levels of radon, since radon is typically the most concentrated on the lowest floor of a building. If the result comes back showing the presence of radon, additional testing is recommended, and you may wish to consider the Exposure Method for this testing.

Exposure Method

To determine the exposure risk to radon, you will want to test the radon level in the home in a location where people spend time. Radon is only a health risk if someone is occupying the area where it is present and breathing the radon. The exposure method seeks to find the radon level in places where people are spending time. 

Because radon levels often vary in a building from room-to-room, this method may require more tests to adequately understand the radon level in a building. You may need to test each occupied room, especially if the rooms are far apart from each other or on different floors of a building. The exposure method is best suited for follow-up testing where an initial screening test has been performed and you are seeking more information to make an informed decision regarding mitigating the home.

If you wish to conduct a limited exposure test, place at least one test in the lowest level of the home which is regularly inhabited, ideally in a room where people spend a lot of time. For example, if you have an unfinished basement, you may wish to test your master bedroom on the ground floor. This is very similar to the Screening Method; however, you are choosing not to test the lowest level of the home because it is not currently inhabited.

If you wish to conduct a thorough exposure test, place one test in each occupied room in the home. This is the best way to ensure you know the exact radon level in each room and therefore the exposure risk for living in that room.

Because assessing exposure is complex, the best placement strategy for this method can be difficult to determine. Radon levels can and often do vary from room-to-room, particularly on upper floors of a building, so when using this method, it is strongly recommended to test every occupied room.