Learn. Radon Facts.

Radon is a colorless, odorless, tasteless radioactive gas that seeps up from the earth.  When inhaled, the radioactive particles can damage the cells that line the lungs.

Long-term exposure to radon can lead to lung cancer.  The U.S. EPA attributes over 20,000 lung cancer deaths each year to radon, making it a serious health concern for all Americans.

Where does radon come from?

Most often, radon comes from the soil.  Radon is formed by the natural breakdown of uranium, which is found in nearly all soils.  Uranium is an unstable element, so it continuously decays until it forms a stable element - lead.  Along the way it forms radium, which disintegrates into radon, a radioactive gas.

How does radon enter a home?

Because radon is produced from soil, it is present nearly everywhere.  Soil is porous, so radon and other soil gases are able to move up through the dirt and rocks and into the air we breathe.

Without proper ventilation, radon can accumulate in indoor spaces, including your home, office, school, etc.

Two factors that determine how much radon will accumulate are pathways and air pressure. Because these factors differ from home to home, indoor radon levels vary from home to home.


Pathways are routes that gasses use to enter your home (openings between the soil and the home).

Radon can enter your home through the following pathways:

•   •  cracks in concrete slabs
•   •  uncapped hollow-block foundations
•   •  floor-wall joints
•   •  mortar joints
•   •  pores and cracks in concrete blocks
•   •  weeping drain tile (if drained to an open sump)
•   •  exposed soil (in a sump or crawl space)
•   •  loose-fitting pipe penetrations
•   •  building materials (brick, concrete, rock, etc.)
•   •  well water

Any home can have a radon problem, regardless of foundation type.

A basement provides a large surface area in contact with the soil material.  Radon can enter through cracks in the concrete, floor-to-wall joints, control joints, etc.  Exposure to radon can be especially high for people who use their basements as living space.

Like basements, homes with slab-on-grade foundations have many openings that allow radon to enter.

Homes with crawl spaces can also have elevated radon levels.  Radon-laden soil gases can be drawn into the home due to negative air pressure vacuums.

Homes generally operate under a negative air pressure, especially during the heating season.  The air pressure inside your home is typically lower than the surrounding air and soil, creating a vacuum that pulls soil gases into the home through the pathways.  While the ground and the home may be frozen or soaked by rain, the gravel and soil underneath the home remain warm and permeable, attracting radon gas from the surrounding soil.

Factors that contribute to a home's air pressure changes include:

  •  Stack effect - Warm air rises to upper portions of the home and is replaced by cooler, denser outside air (some of which comes from the soil).

  •  Down wind draft effect - Strong winds create a vacuum on the downwind as they blow past a home.

  •  Vacuum effect - Combustion appliances (furnaces, hot water heaters, fireplaces, etc.), exhaust fans, and vents can remove a significant amount of air from a home.  As indoor air is exhausted, outdoor air enters the home to replace it.  This replacement air often comes from the soil underneath the home.