You are sending a link to... What about Radon Gas?
Eddie Hutton, Partner, answers the question this way.
Everyone needs to think about radon gas. Radon is a radioactive, colorless, odorless, tasteless gas. Some say radon causes lung cancer. Radon gas comes out of the ground and is produced by the decay of radioactive particles such as uranium found in the limestone that underlies Middle Tennessee. If you have radon gas you need to ventilate your crawl space or basement to remediate your exposure to the gas. The photos show one way with black plastic covering the ground in the basement of a 1925 house. Outside a powered fan pulls air from under the plastic and expels it into the atmosphere. You can tell if you have radon that exceeds safe limits by going to your local hardware store and picking up a radon gas detector kit. The photo below shows an example of one type kit. More information here.