Helium, Neon, Argon, Krypton, Xenon, Radon
Helium can be absorbed into the body. SIde Effects: Dullness, Headache, and Dizziness.
On loss of containment, this gas can cause suffocation by lowering the oxygen of the air in certain areas.
Helium was found in space by Pierre Janssen, and Norman Lockyer in 1895.
Radon is radioactive, rarely occurs in a natural environment.
Most Radon compounds found in the environment are caused by human activity.
Radon enters the environment through the soil, through uranium and phosphate mines, and through coal combustion.