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Air Quality

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

Why is radon a concern?

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.

Is radon causing me to feel sick (i.e. coughing, headaches, weakness, etc.)?

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.

How do we know that radon causes 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

How do I test for radon? Where can I get a radon test kit?

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.

Radon test kits are very time-sensitive and must be mailed within 3-5 days after the test kit is sealed up. Failure to follow the instructions can cause the lab to invalidate the results. Be sure to carefully read and follow the instructions that come with the test kit.

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.

What do my radon test results mean?

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.

What is the difference between short-term and long-term test kits?

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.

How do I get the results for my radon test?

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.

Am I required to test for radon?

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

Can radon affect my drinking water?

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

How can radon be mitigated in my home?

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:

How do I find a reliable contractor for radon mitigation?

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

Is there any financial assistance available for radon mitigation?

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

What should homebuyers and sellers know about radon?

Colorado law requires that homeowners disclose to buyers if they are aware of the radon levels in the home they are selling. 

After January 1, 2005, all new single-family and duplex housing in Fort Collins must be equipped with a radon reduction system during construction. The system frequently relies on passive ventilation and can be concealed within the internal skeleton of the home. Homeowners should test for radon and if further reduction is needed, have an in-line fan installed in the space provided.

Fort Collins Municipal Code Requires that every seller shall provide radon information to the party purchasing the property prior to the execution of any contract for such property. The Radon Information Brochure (Spanish)  is usually included as part of the transaction. Although City code does not require radon testing or mitigation, we urge everyone to test their home for radon.

To learn more, call Fort Collins Building and Zoning at (970) 221-6760.

Can I make my landlord mitigate for radon?

There is no city, county or state ordinance that requires any homeowner, including landlords to mitigate radon.  If you've tested and found high levels and your landlord refuses to mitigate for radon, Neighborhood Services offers mediation for landlord-tenant issues.  For reference take a look at the City of Fort Collins Landlord and Tenant Information page which include links to the Landlord Tenant Handbook.

Are there any HOA restrictions on radon mitigation systems?

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

Where does radon come from?
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.

What are radon levels in Fort Collins?

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.  

How is radon measured? What is pCi/L?

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.