Finishing an unused lower level such as a basement can provide your family with additional living space. You can add a mother-in-law suite, a theater room or man cave in the extra space. Before you move into or regularly use those lower levels, it is a good idea to test for radon.
There are at least two reasons it is smart to test the lower level after you’ve completed construction. First, the construction can release new levels found in the recently disturbed soil. Second, the newly finished are of the home will be used more now and have more movement in the air. Both of these can change previous readings.
A second test provides an accurate level for those newly used spaces and ensures the radon levels are acceptable. If they are too high, you can plan to mediate the amount of radon in the basement before it moves to the rest of the home.