Radon is a radioactive chemical gas found in the ground from the natural breakdown of uranium in a property's soil. This chemical then moves up to the air and gets into houses and buildings through cracks on their foundations.
It is hazardous, as it can increase the risks of cancer and other horrible illnesses. Therefore, it is vital to get each property tested on its radon levels before buying one.
A test done on another house from the same neighborhood isn't reliable enough to legally sell the house, making it extremely important for every home to get tested.