What is Radon?
Radon is a natural occurring chemically inert gas. It comes for the radioactive decay of common uranium in soil that enters building directly beneath and a few meters around the foundation. Radon can enter all types of buildings and the main concern is when radon has the chance to accumulate. Tight homes do not cause radon; they increase the likelihood of radon lingering instead of escaping through ventilation.
The Health Risk
Radon is an unstable atom and will break down into a family of elements called radon decay products. These decay products attach to the surface of dusts and become logged in the lungs. When exhaled, the radon leaves but the decay products remain in the lungs which have been proven to cause lung cancer. The chance of lung cancer increases greatly for smokers as they already have damaged, weaker lungs. For a non smoker, if exposed to the minimum suggested EPA actionable level of 4 pCi/L, there would be the equivalent risk ratio of dying in a car crash.
How Radon Enters Buildings
There are many ways radon can enter a building. The main reason is that buildings naturally create vacuum effects. Vacuums are caused by either temperature induced stack effects or mechanical exhaust systems. Their are typically four ways radon enters a structure: Vacuum effects, water, diffusion, and emanation.
The Vacuum Effect (90+% of Radon)
Mechanical Devices such as Stove Fan and Bathroom Fans
A good way to visualize is to imagine a bathroom fan or over-the-stove fan turned on and creating a negative pressure in the home. If it is winter, the windows and doors in the home closed tight so a lot of air is being drawn from the cracks and holes in the basement foundation to the radon laden soil below. If you basement is a dirt crawl space, it can have a much greater accumulation of radon gas.
A fireplace will drawn a small amount of air from your home and create enough vacuum effect tto increase radon amounts.
Radon from Water
Radon can dissolve in groundwater and readily degases when brought into a building causing an additional amount of radon to enter the air. On average 10,000 pCi/L in water will add 1 pCi/L into the air. The health concern is from the additional amount of radon in the air, not ingestion.
Where radon diffuses from soil through a slab due to concentration gradients. This is typically a small contributor.
This is when a building material contains uranium or radium and is brought into a building. This is also a low contributor but deserves attention.