A radon inspection is necessary if you are buying or selling a home. Radon is a radioactive gas that comes from the earth and can cause lung cancer. The only way to know if your home has a high level of radon is to have it tested. Testing is easy and only takes a few minutes. It's important to test your home, even if you don't think it has a problems, because 9 out of 10 homes have high levels of radon.