The first step is to perform a radon test. The only way to know if your house has elevated levels of radon is to either have a professional (CRM) test done, or run a DIY test kit. If high levels of radon are present in the home then a professional should be consulted to figure out how to reduce those levels. The most common method is called a Sub Slab Depressurization System or Radon Mitigation System which is installed to prevent radon from entering the house to begin with.