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Radon Frequently Asked Questions#

Radon is a class 'A' carcinogen and long-term exposure to elevated levels has been linked to radon-induced lung cancer.   About half or all home tested in Fort Collins have radon levels above the EPA action level of 4 pCi/L.  Learn more below about Radon or visit the Radon Home Page and Radon resources library.

Radon Health Risks#

Radon is a class 'A' carcinogen (pollutants with adequate human data indicating that it causes cancer in people). Polonium-218 and Polonium-214 are alpha-emitting radon decay products that have been identified as the primary cause of radon-induced lung cancer. Alpha particles are very effective at causing DNA damage.

Your chances of getting radon-induced lung cancer depends on how much radon is in your home, the amount of time you are exposed to it, and whether you are a smoker. Long-term radon exposure is the leading cause of lung cancer in individuals who have never smoked. There were an estimated 21,000 deaths in the U.S in 2018 due to radon-induced lung cancer.

The Surgeon General has warned that radon is the 2nd leading cause of lung cancer in the US. Only smoking causes more lung cancer deaths.

There are currently no known symptoms of short-term exposure to radon at the levels typically found in homes. It takes years of exposure at relatively high levels, and the known symptoms are similar to those for smoking related lung cancer.

The EPA's Health Risks of Radon page contains detailed information about the health risks. In addition, there have been numerous studies done on the linkage between lung cancer and exposure to radon. Here are a few of the key papers:

Radon Testing#

The City of Fort Collins sells discounted short-term ($6) and long-term ($20) radon test kits and are available for purchase at the Fort Collins Senior Center (1200 Raintree Drive). If you reside outside the City limits you can order a radon test kit from the CDPHE.

Be sure to carefully read the instructions that come with the test kit. Failure to follow the instructions can also cause the lab to invalidate the results.

Radon test kits are very time-sensitive and must be mailed immediately after the test kit is sealed up. The lab will invalidate the results if they don't receive the test kit within 8 days.

The CDPHE has published Measuring and Mitigating Radon in Colorado: A Technical Guidance for Colorado Building Conditions. This is a great resource that covers the science behind radon, and guidance for measurement and mitigation systems.

According to the EPA: "People should not have long-term exposure to indoor radon levels of 4.0 pCi/L or more.  4.0 pCi/L of radon is an economic guidance rather than a level below which no risks exists".  It is up to you to determine what level of radon is acceptable in your home.  For reference:

  • 4.0 pCi/L     EPA threshold for mitigation
  • 2.7 pCi/L     World Health Organization threshold for mitigation
  • 2.0 pCi/L     Target level for radon mitigation repairs
  • 0.4 pCi/L     Average radon level in outdoor air

The EPA Citizen's Guide to Radon contains more information about radon in the home, and how to test and read the results, and information about the health risks of living with radon.

Short-term tests typically run from 3 to 7 days and require closed house conditions for the duration of the test.   These kits work by capturing radon in charcoal which is then analyzed by the lab.  These kits provide a quick snapshot of the radon present during the test and are usually a good indication of whether more comprehensive testing is needed.

Long-term test kits run from 90 days to a year and are conducted with the home under normal living conditions.  These test kits typically are alpha track detectors which use a film that gets etched by alpha particles.  The lab analyzes these kits by counting the number of alpha tracks.   These tests give a more representative picture of the radon levels in a home over time.

Continuous or Active radon monitors are electronic devices that integrate continuous radon measurements over time.  They run constantly but usually require some type of periodic calibration.

If you're interested in the technical details of how the lab measures radon from the test kits, take a look at the Radon Analysis Methods: Analytical Procedures and Comparison article from AirChek Inc.

The testing lab will email your results to you as soon as they process your test kit. If you don't hear from them within a couple weeks, contact us and we can usually track down the result for you.

No, although City code does not require radon testing or mitigation, we urge everyone to test their home for radon.

If you use a well for your drinking water supply, radon can also enter your home through well water. If your home has a high radon level in the air (4 pCi/L or more) and you have a well, call the Safe Drinking Water Hotline at 1-800-426-4791.

Radon Mitigation#

The most common approach for radon mitigation is Active Sub-Slab Depressurization. The idea is to create a vacuum under the foundation or crawlspace which draws out and exhausts radon gas outside the building. These systems can be active or passive, where a passive system vents radon through a pipe that extends from the soil to the roof and acts like a chimney to create a slight vacuum on the soil. An active system simply adds a fan to the passive system to forcibly draw radon from the soil.

To be effective, any cracks or openings in the foundation must be sealed. Crawlspaces and sumps are two of the main culprits for allowing radon gas into the house directly through exposed soil.

Here are some great resources for learning about the technical details of radon mitigation systems:

The EPA's Consumer's Guide to Radon Reduction is a good resource for what to expect from a radon mitigation contractor.  The National Radon Proficiency Program (NRPP) maintains a list certified radon contractors in Colorado.

Find a Certified Radon Professional

Low Income Radon Mitigation Assistance (LIRMA)#

Take a look at the Colorado Department of Public Health and Environment (CDPHE) site to learn about Financial Assistance to Reduce Radon in Your Home.   CDPHE can provide financial assistance up to $1500 to inidviduals with low-income status for radon mitigation services.   Homeowners must be a Colorado resident, occupy the property as their primary residence and qualify as a low-income household.   Funding is limited and starting in July until funds run out for the state fiscal year.

View the LIRMA Policy and Procedures Manual

Radon in Real Estate and Rentals#

Colorado law requires that home sellers inform buyers if they are aware of the radon levels in the home they are selling using the Sellers Property Disclosure form

Colorado also requires that the seller shall provide the most recent brochure published by CDPHE that provides advice about radon in real estate transactions. The most recent radon brochure can be found on the CDPHE Radon webpage.

Before a tenant signs a lease for a rental property, the landlord must provide this brochure and provide the tenant with a document stating:

  • Tenants should have an indoor radon test performed before leasing the property and if elevated levels are found, request the landlord to mitigate
  • Any knowledge the landlord has regarding the radon levels of the property including previous testing, test results, and information about any installed radon mitigation system.

A tenant can break the lease if:

  • A landlord fails to make this disclosure or
  • A landlord does not make a reasonable effort to mitigate elevated levels of radon within 180 days after being notified that a radon measurement professional has found elevated levels of radon.

A renter can test their own unit. If elevated levels are found, notify the landlord in writing and request mitigation. Landlords are not legally required to install a mitigation system.

We are not aware of any HOAs in Fort Collins that have denied a homeowner the ability to install a radon mitigation system.  If you run into a problem with your HOA, get in touch with Neighborhood Services to see if community mediation can help solve the problem.

Other Questions#

Uranium to radon decay chain

Radon is a radioactive gas that comes from the natural decay of uranium that is prevalent in our soils.   The chart above shows a slice of the decay chain from uranium to lead and indicates the type of decay (alpha) and the half life of each element in the chain.

For more information on radioactive decay, view the EPA discussion on U-238 decay chain.

The City of Fort Collins has been providing radon test kits to residents since 1997 and has accumulated thousands of test results in our database from individual residences. The latest trends show that about half of the homes tested have radon levels above 4 pCi/L and about 15% of homes tested have pCi/L levels above 10 pCi/L.

In 1993, the EPA surveyed all counties in the country and classified them as Zone 1, Zone 2, or Zone 3.  A Zone 1 classification means that average indoor radon levels are above 4.0 pCi/L.   Refer to the EPA's National Map of Radon Zones for more details.

The most recent survey from CDPHE shows that all counties in Colorado are classified as Zone 1.  Take a look at the CDPHE Map and Datasets for details of county by county indoor radon levels in Colorado.  

The concentration of radon gas is measured in the U.S as picoCuries per liter of air (pCi/L). A picoCurie (pCi) is 1 trillionth of a Curie, and a Curie is defined as the amount of radioactive decay of radium 226 over a 24-hour period. One pCi of radon is about 2.22 radioactive disintegrations per minute. The EPA action level of 4 pCi/L amounts to about 12,672 radioactive disintegrations per liter of air during a 24 hour period.