Radon

Radon is an invisible, radioactive atomic gas that results from the radioactive decay of radium, which may be found in rock formations beneath buildings or in certain building materials. Radon is one of the most pervasive serious hazard for indoor air, probably responsible for tens of thousands of deaths from lung cancer each year.  There are relatively simple tests for radon gas, but these tests are not commonly done.

Radon is a heavy gas and will accumulate at the floor level. Building materials can actually be a significant source of radon, but little testing is done for stone, rock or tile products brought into building sites.  Radon accumulation is greatest problem for well insulated homes. The half life for radon is 3.8 days, indicating that once the source is removed, the hazard will be greatly reduced within a few weeks.

Radon levels can be reduced by sealing concrete slab floors, basement foundations, water drainage systems, or by increasing ventilation. They are usually cost effective and can greatly reduce or even eliminate the contamination and the associated health risks.