48-Hour Continuous Radon Testing. A Radon Monitor is dropped of 2 days before the inspection if possible so the client will have the results at the time of the inspection. Radon is a naturally occurring gas that comes from the soil and often gets trapped inside your house. If you have a basement, it is highly recommended to have your home tested. Radon is the second leading cause of lung cancer. In Michigan 1 in 4 homes are expected to have a Radon problem.