Radon (Rn) is a cancer-causing radioactive gas found in many communities' ground water. Radon is a colorless, odorless, naturally occurring, radioactive, inert, gaseous element formed by radioactive decay of radium (Ra) atoms.

The atomic number is 86. Although other isotopes of radon occur in nature, radon in indoor air is almost exclusively Rn-222.

-See also:
"Radon" is in the UNSPSC Code "12142002"
Radon gas Rn

"Radon" is in the NAICS Code "23899"
(Inofficial Code)
· Radon testing-are classified in Industry 541380, Testing Laboratories;

Other definition:
Radon is a colorless, odorless naturally occurring radioactive gas formed by the breakdown or decay of radium or uranium in soil or rocks like granite. Radon is fairly soluble in water, so well water may contain radon.