Radon enters a home through the lowest level in the home that is in contact with open ground. Typical entry points of radon into homes are cracks in solid foundations, construction joints, cracks in walls, gaps in suspended floors, gaps around service pipes, cavities inside walls, and the water supply.
Our inspections are done using a Continuos Radon Monitor which is left in a closed-house condition for a minimum period of 48 hours. Closed-house conditions mean keeping all windows closed, keeping doors closed except for normal entry and exit, and not operating fans or other machines which bring in air from outside.
Again, for all of the info you could ever hope for on radon and the testing and mitigating processes, you can click HERE to see the EPA's website about it.