Radon is a radioactive, invisible, odorless and colorless gas which can infiltrate
your home through small cracks in the basement or from high radon levels in water
if you are have a private well. In rare cases it can come from radioactive decay
of solids in concrete, gypsum or other building materials.
Radon is a decay element
from Uranium in the rocks underneath your house. Although Uranium is a metal and
therefore sticks to the rocks, when it decays in several steps to the metal Radium-226
and from there to Radon-222 it becomes a rare gas and escapes through the natural
cracks in the rocks upwards driven by the natural pressure gradient in the rock and
soil underneath the house..
Radon is approximately 7 times as heavy as the Oxygen
molecule but because it is a rare gas (meaning that it is not chemically active,
as are the other gasses Helium, Neon, Argon, Krypton and Xenon) it will be easily
kicked around by other air-molecules and be found throughout the house. Typically
the Radon concentration in a house one level higher than the lowest lived-in level
is 70%, although this distribution is very broad, from 25% to 100%.