You cannot see it, smell it or taste it. Each time this multi step decay process takes place, radioactive alpha particles are emitted. It is these alpha emitters that are responsible for the damage to our health. When radon is present in the soil that surrounds our homes it can be drawn into the basement by the negative pressure found in the lower levels of all structures. This drawing effect pulls radon into the home and is then generally distributed throughout the house by the heating and cooling system.
Radon enters easily because it is so small.
As an example, the reason helium balloons get smaller after you buy them is because helium molecules are smaller than the molecules that make up the wall of the balloon. The helium passes right through. Radon is exactly the same size as helium and can easily pass through cracks, openings and most of the porous materials used to construct the foundations and floors of our homes. Radon is second only to cigarette smoking as the leading cause of lung cancer death. Both are preventable.