radon gas detector

https://www.google.com/maps/d/u/1/edit?mid=13vaGCM6XDFQPDckIMSd6_hUf5PWr5EvC&ll=36.14683223511943%2C-86.76655149999999&z=10

Radon can not be seen, scented, felt, or otherwise spotted, apart from with an examination. That's why, according to the EPA, the only means to recognize for certain if you have a radon issue is to examination.