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  • Writer's pictureAleks Webster, PhD, CPI, RME

What is radon? Where does it come from? Why should we care about it?

When a client calls to schedule a home inspection, I almost always ask if they would like to include a radon test. These are some of the responses I have received.

“Why should I get a radon test? I don’t have a basement!”

“Radon… it’s a conspiracy to make us fearful about something that doesn’t matter.”

“My neighbor’s house tested low for radon. I’m sure my house is the same.”

What is Radon?

Radon is an invisible, odorless, tasteless, naturally occurring, ubiquitous, radioactive, potentially deadly gas that occurs virtually everywhere.

Where does it come from?

Radon gas is produced from series of decay processes that begin with Uranium, a

Diagram of Uranium decay chain
Uranium decay chain

radioactive metal found in soil and rocks. As Uranium decays, it releases 2 protons and 2 neutrons bound together, known as an ionized Alpha particle. The resulting by-product of this decay is Thorium, another radioactive metal. This Alpha particle releasing decay process continues, with Thorium becoming Radium, Radium becoming Radon, Radon becoming Polonium, and Polonium becoming Lead. There are other types of decay processes that occur in this chain that also create Astatine, Bismuth, Thallium, and Mercury, many of which are highly toxic.

The released Alpha particles, in general, are not dangerous to life due to their inability to penetrate the skin and their short range of absorption. However, they are dangerous if ingested or inhaled, as alpha radiation is the “most destructive form of ionizing radiation”. When you breathe in radon, radioactive particles from radon gas can get trapped in your lungs. Over time, these radioactive particles increase the risk of lung cancer.

Illustration of low to high soil permeability

Radon gas moves through the rocks and soil. The ease in which radon gas moves to the surface is dependent on the differences in soil permeability. This is the major reason why two houses right next to each other may have completely different radon gas levels.


The other potential reasons that radon level differences inside the home occur are:

· Increased permeability around the basement, foundation, and/or slab

· The presence of openings in the house’s foundation

· Differences in air pressure between the soil and the house

When a house is constructed, excavation disturbs the soil underneath and around the house. These disturbed areas are then backfilled with less permeable gravel and soil, which allows the radon gas to travel towards the house. Once at the foundation, cracks, seams, openings, or uncovered soil in the crawl space or basement provide the path for radon to enter the home. And, finally, air pressure inside the house is typically much lower than outside air. Higher pressure air naturally travels towards lower pressure spaces to come into equilibrium.

Why should we care about it?

Exposure to Radon gas is the number one cause of lung cancer among non-smokers, according to EPA estimates. Overall, radon is the second leading cause of lung cancer and is responsible for about 21,000 lung cancer deaths every year. About 2,900 of these deaths occur among people who have never smoked.

Ways to reduce Radon levels in your home…

1. Hire a licensed Radon Measurement Professional (RMP) to test your home for Radon.

2. If the test levels are above 4 picocuries per liter (pCi/L) of air (EPA recommended standard), hire a qualified professional to install an active radon mitigation system.

3. Seal and/or caulk all foundation cracks and other openings.

4. Install a proper vapor retarding barrier in crawl spaces and/or basements where there is exposed soil.

5. Increase air flow in your house by opening windows and using fans and vents to circulate air.

5. Always test your radon levels after making any of these changes.

NOTE: As of July 1, 2022, all individuals conducting radon measurement or radon mitigation are required to be licensed by Colorado’s Department of Regulatory Agencies (DORA).

Have more questions? Call us, 970.685.1832 or email us,

Schedule your home’s radon test TODAY!


Center for Disease Control and Prevention, “Protect Yourself and Your Family from Radon”.

Colorado Department of Public Health and Environment, “Radon”.

National Institute of Environmental Sciences, “Radon

Otton, James K., U.S. Department of the Interior / U.S Geological Survey, “The Geology of Radon”, 1992.

United States Environmental Control Agency (EPA), “Radon

Wikipedia – “Alpha Particle

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