Radon is a colorless, odorless, and tasteless gas. It's the decay product of radium, a radioactive element found in rocks and soil.
According to the Surgeon General, radon is the second leading cause of lung cancer (after smoking) in the United States today.
Radon can be found all over the U.S. and tends to concentrate in enclosed spaces, such as underground mines or houses.
Radon and Real Estate Transaction
The Environmental Protection Agency (EPA) recommends that each house should be tested for the presence of radon.
A radon test is quite inexpensive and is performed with a calibrated sensor.
Check out this 'Home Buyer's and Seller's Guide to Radon' by the EPA and this 'Home Buyer Radon Protection Guide' aboout the different scenarios you can face during a real estate transaction.