Radon can enter via cracks in the foundation walls and/or floor slabs. It can also enter through other openings, including:

• unfinished floors (dirt);
• construction joints;
• gaps around service pipes;
• support posts;
• window casements;
• floor drains;
• sumps; and/or
• cavities inside walls.

Indoor radon levels are the result of a number of interconnected factors including the property's bedrock type, soil type, soil moisture level, seasonal freezing and thawing activity and the home's design, construction and use.