Radon-222

Radon-222 (Rn-222) is a radioactive isotope of radon, a noble gas that occurs naturally in the environment as a decay product of uranium and thorium. It is colorless, odorless, and tasteless, making it undetectable without specialized equipment. Radon-222 has a half-life of about 3.8 days, meaning that it decays relatively quickly compared to some other radioactive isotopes.