Radon can go into residences through cracks in floors, structures, or walls, and also accumulate inside. It can also be released from building materials, or from water acquired from wells that contain radon. Radon levels can be greater in residences that are well shielded, tightly sealed, and/or built on dirt abundant in the components uranium, thorium, as well as radium. Basement and also initial floors typically have the highest possible radon levels because of their nearness to the ground.