Radon: Frequently Asked Questions
Updated October 2009
What is radon?
Answer: Radon is a naturally occurring, radioactive gas found all over the United States. Radon moves through the ground to the air above, and into buildings through foundation cracks, other structural openings, and well-water. Radon trapped inside homes can result in serious adverse health effects.
How common is radon?
Answer: It is estimated that one out of 15 homes in the U.S. has an elevated radon level.
How do I know if I have a radon problem?
Answer: Radon is colorless, odorless, and tasteless, so radon can only be identified through proper testing. However, certain geographic regions have a higher potential for elevated indoor radon levels than others. The EPA’s Map of Radon Zones can be viewed at: www.epa.gov/radon/zonemap.html.
Can a radon problem be fixed?
Answer: Yes, even very high levels can be effectively remediated.
How do I test for radon?
Answer: Generally, you can test for radon yourself, or use a qualified radon professional. Various testing methods are used depending on individual need and time constraints. Testing can be passive (using charcoal canisters, alpha-track detectors, etc.) or active (continuous radon monitors). Passive testing materials are inexpensive and readily available at hardware and building supply stores. Active testing is generally only performed by radon professionals and more expensive than passive methods, but may be more reliable.
How long does testing take?
Answer: Testing time varies. Short-term testing lasts from 2 to 90 days. Long-term testing lasts greater than 90 days. Note: Every radon test should last a minimum of 48 hours.
What is a typical radon level?
Answer: The average indoor radon level is 1.3 pCi/L, and the average outside radon level is 0.4 pCi/L.
What constitutes an elevated radon level?
Answer: The EPA-established action level is 4 pCi/L or more. In September 2009, the World Health Organization (WHO) lowered their action level to 2.7 pCi/L or more. The WHO actions do not supersede or otherwise affect the EPA’s guidance concerning radon in the U.S. The latest information regarding EPA action levels can be found at www.epa.gov/radon/realestate.html.
What should I do if testing reveals an elevated radon level?
Answer: The EPA recommends, but does not require, that you contact a qualified radon-reduction contractor and remediate the property where radon levels of 4 pCi/L or more are detected. EPA recommends that you consider remediation where radon levels are between 2 and 4 pCi/L, depending on individual circumstances. EPA notes that it is not technologically achievable to reduce radon levels to 2 pCi/L or less in all buildings.
How do I remediate my property?
Answer: First, select a qualified radon-reduction contractor. Many states require such professionals to be licensed or otherwise certified, and can provide you with a list of experienced providers. Any remediation measures undertaken must conform to your state’s regulations and building codes. In those states without remediation regulations, abatement efforts should conform to EPA’s Radon Mitigation Standards, available at www.epa.gov/radon/pubs/mitstds.html. For state and regional information about remediation contractors, see www.epa.gov/radon/fixyourhome.html.
What does radon remediation involve?
Answer: The right remediation method depends on the building design, construction materials, and other factors. Typical methods include sealing cracks and other openings in the foundation (although the EPA does not recommend the use of sealing alone to reduce radon levels), and the installation of a vent and fan system.
Do I have to remediate the property?
Answer: There are currently no laws requiring radon remediation. However, unacceptable radon levels can frustrate any effort to sell, transfer, or finance the property. Also, high radon levels can expose a property owner to resident complaints and uninhabitablity claims.
Is testing and disclosure of a property’s radon level required by law?
Answer: Yes and No. Some states require the disclosure of known, environmental hazards (including radon) during a sale or transfer of the property. However, these laws do not require a property owner to conduct radon testing; you must only disclose the results of prior testing. But, note, that many lenders do require radon testing. For more information about your state’s specific radon laws, see:
In addition, OSHA regulations limit employee exposure to radon and could require employers to survey or test the workplace environment. However, the OSHA occupational exposure limits for radon (100 pCi/L) are much higher than the EPA action levels. For information on OSHA radon policy, see www.osha.gov/dts/sltc/methods/inorganic/id208/id208.html.
The EPA recommends radon testing for all homes below the 3rd floor, so are high-rise apartment buildings immune from radon problems?
Answer: No. Radon can still present a problem in high-rise structures, since the gas can be distributed throughout the building via elevator shafts, HVAC systems, etc.
Is there a way to prevent radon intrusion?
Answer: Yes. There are proven radon-resistant building techniques, which can both mitigate radon levels and improve building performance in terms of energy efficiency and moisture control. Typical techniques include the use of: gas-permeable layers, plastic sheeting, sealing and caulking, vent pipes, and junction boxes. For more specific information, see www.epa.gov/radon/rrnc/index.html.
How costly are these prevention techniques?
Answer: Incorporating radon-resistant techniques into new building designs has proven to be more cost-efficient than installing a radon-remediation system in an existing structure. The cost depends on the size and characteristics of the property, but the following EPA estimated costs provide a useful illustration:
- Cost of using radon-resistant techniques in building a new home = $250-$750
- Cost of remediating radon from an existing property = $800-$2500.
In addition, radon mitigation is increasingly required in new construction by building codes and green building standards.