Radon Information Toll-free Hotline:
Frequently Asked Questions
- What is radon?
- Is radon common in Montana?
- What health effects are associated with radon exposure?
- What is a "picocurie" (pCi)?
- Why is 4 pCi/L the recommended action level for radon?
- What is the "acceptable" level of radon in air?
- How often is indoor radon a problem?
- How does radon get into a building?
- Can the radon level in a building's air be predicted?
- I just found out my house has elevated radon gas levels. Should I see my physician?
- Do radon levels increase with the age of a home?
Testing Air for Radon
- Why should I test my home for radon?
- Who can test a building for radon?
- Where should home testing be done?
Radon Resistant Construction
- What are radon-resistant features?
- When should radon-resistant construction be considered?
- What are the benefits of radon-resistant construction?
- How much does it cost to reduce radon in an existing home?
- Who should I hire to install radon-resistant features?
- Should a home built with radon-resistant features be tested?
- What are the codes or standards for radon-resistant new construction?
- Are there recognized methods for testing soil gas to estimate radon potential in a future building?
Radon Testing During Real Estate Transactions
- What information is available regarding radon and real estate transactions?
- I'm buying a house. Should I have it tested for radon?
- I'm selling a house. Should I have it tested for radon?
- Can vacant houses be tested for radon?
- The seller of the house I want to buy disclosed a radon level of 2. Should this be a deterrent to buying?
Mitigating Radon Problems
- What is a radon mitigation system?
- What are the benefits of radon mitigation?
- What can be done to reduce radon in a home?
- How much does it cost to reduce radon in an existing home?
- Who should I hire to correct a radon problem?
- Will any more testing be needed after a radon mitigation system has been installed?
- Are funds available to reduce high radon levels in rental housing?
Radon in Water
- How does radon get in water?
- Does radon in drinking water pose a risk?
- Should drinking water be tested?
- What do the results of a water test mean?
- What levels of radon in water should I be concerned about?
- How is radon removed from water?
Radon is a radioactive gas. It is has no color, odor, or taste. Unless you test for it, there is no way of telling how much is present.
Radon is formed by the natural radioactive decay of uranium in rock, soil, and water. Low levels of uranium occur naturally in Earth's crust and can be found in all 50 states; thus, radon can be found throughout the United States as well. Once produced, some of the radon gas moves up through the ground into the air above and some remains below the surface where it dissolves in the water that collects and flows under the ground.
Radon has a half-life of about four days—that is, half of a given quantity of it breaks down every four days. When radon undergoes radioactive decay, it emits ionizing radiation in the form of alpha particles. It also produces short-lived decay products, often called progeny or daughters. Some of these are also radioactive.
Unlike radon, the progeny are not gases and can easily attach to dust and other particles. Those particles can be transported by air and inhaled. The decay of progeny continues until stable, nonradioactive progeny are formed. At each step in the decay process, radiation is released.
Sometimes, the term radon is used in a broad sense, referring to both radon and its radioactive progeny. When testing radiation from the progeny, the measurements are usually expressed in working level (WL) units. When testing radiation from radon, the amount is usually expressed in picocuries per liter of air (pCi/L).
Radon can be found in every state, including Montana. The geology of an area typically determines the concentrations of radon found. The U.S. EPA has documented the radon potential of Montana and defines the zones as follows.
The U.S. EPA defines Montana’s radon potential as follows:
Zone 1 counties have a predicted average indoor radon screening level greater than 4 pCi/L (picocuries per liter) (red zones)
Zone 2 counties have a predicted average indoor radon screening level between 2 and 4 pCi/L (orange zones)
Breathing radon does not cause any short-term health effects such as shortness of breath, coughing, headaches, or fever.
A pCi is a measure of the rate of radioactive decay. One pCi is one trillionth of a curie, 0.037 disintegrations per second or 2.22 disintegrations per minute. Therefore, at 4 pCi/L (picocuries per liter, the EPA's recommended radon action level), there will be approximately 12,672 radioactive disintegrations in one liter of air during a 24-hour period.
Finally, a cost-benefit analysis performed in 1986 indicated that an action level of 4 pCi/L results in a cost of about $700,000 per lung cancer death saved. If the action level was set at 3 pCi/L, the cost would be $1.7 million, and if set at 2 pCi/L, the cost would be $2.4 million per lung cancer death saved.
Homeowners can further reduce their potential risk by mitigating homes that are below 4 pCi/L.
Nearly one out of every fifteen homes has radon concentrations at the level the EPA considers to be elevated, 4 pCi/L or greater. The U.S. average radon-in-air level in single family homes is 1.3 pCi/L. Because most people spend as much as 90 percent of their time indoors, indoor exposure to radon is an important concern.
- Cracks in floors and walls
- Gaps in suspended floors
- Openings around sump pumps and drains
- Cavities in walls
- Joints in construction materials
- Gaps around utility penetrations (pipes and wires)
- Crawlspaces that open directly into the building
A map of radon zones has been created to help national, state, and local organizations target their resources and implement radon-resistant building codes. However, the map is not intended to be used for determining if a home in a given zone should be tested for radon. Homes with elevated levels have been found in all three zones.
In addition, indoor radon levels vary from building to building. Do not rely on radon test results from other buildings in your neighborhood—even ones next door—to estimate the radon level in your building.
Many homeowners who perform their first radon test after several years of occupancy will learn that their homes have radon values of 4 pCi/L or more. This often raises medical questions for them. There is no standard medical screening test at this time to determine if an individual has incurred tissue damage that might increase the risk of lung cancer.
Inform your family physician of your radon exposure. Normally, a chest x-ray is not recommended for radon exposure alone, but your physician will determine the correct course of action for your situation.
No. Elevated radon has been found in brand new homes and homes over 150 years old. The only way to know the radon level in any home, regardless of its age, foundation type, heating system, air tightness, or building materials, is to conduct a test.
Testing Air for Radon
Radon is widely believed to be the second leading cause of lung cancer. Therefore, the EPA and the Surgeon General recommend testing for radon in all homes below the third floor.
Radon has been found in homes all over the United States. Any home can have a radon problem. On average, one out of every fifteen U.S. homes has a problem. The only way to know if your home has a radon problem is to test for it.
Anyone can use a single-use "do-it-yourself" test kit to check their building. Simple to use and relatively inexpensive, these kits can be found in hardware stores and other retail outlets, local health departments, and county extension offices. They are also available through the Internet.
The EPA recommends that you hire a qualified professional to test for radon when you are buying or selling a home. Some states require a specific testing protocol. If you hire a contractor to test your residence, protect yourself by hiring a qualified individual or company.
To determine a service provider's qualifications to measure or mitigate radon, first check with your state radon office. Many states require radon professionals to be licensed, certified, or registered. Most state radon offices can provide you with a list of knowledgeable radon service providers. In states that don't regulate radon services, ask the contractor if they hold a professional proficiency or certification credential.
The EPA recommends that testing be done in the lowest level of the home suitable for occupancy, as this typically is where the greatest radon level may occur. Ideally, the test should be conducted in a regularly used room on that level, such as a living room, playroom, den, or bedroom. Avoid testing in a kitchen, bathroom, laundry room, or hallway, because high humidity and drafty conditions can bias the results from some test devices. Place the testing devices out of the way and do not disturb them while they are sampling. Doing so may alter their results.
If the lowest occupied level is not used much, consider also testing a higher-use area. This may help you more accurately estimate your long-term exposure.
Because most indoor radon comes from naturally occurring radon in the soil, high indoor levels are more likely to exist below the third floor. This is why the EPA recommends testing all homes below the third floor. In some cases, however, high radon levels have been found at or above the third floor due to radon movement through elevators or other airshafts in the building. If you are concerned about this possibility, consider testing for radon on the upper floors.
More information on site selection can be found in the EPA publication, Protocols for Radon and Radon Decay Product Measurements in Homes.
Radon Resistant Construction
Although radon-resistant techniques vary for different foundations and site requirements, the basic elements are:
A: Gas-Permeable Layer—This layer is placed beneath the slab or flooring system to allow the soil gas to move freely underneath the house. In many cases, the material used is a 4-inch layer of clean gravel.
B: Plastic Sheeting—Plastic sheeting is placed between the gas-permeable layer and the slab to help prevent the soil gas from entering the home. In crawlspaces, the sheeting is placed over the crawlspace floor.
C: Sealing and Caulking—All openings in the concrete foundation floor are sealed to reduce soil gas entry into the home.
D: Vent Pipe—A 3- or 4-inch gas-tight or PVC pipe (commonly used for plumbing) runs from the gas-permeable layer through the house to the roof to safely vent radon and other soil gases above the house.
E: Junction Box—An electrical junction box is installed in case an electric venting fan is needed later.
For a checklist of these items, click here: RRNC Checklist (1 page, 381 KB)
For a detailed technical guide to RRNC, click here: See Building Radon Out (84 pp, 5.5 MB)
First find out if you are buying a home in a high radon area. The EPA's map of radon zones indicates areas having the greatest potential for elevated indoor radon readings. Homes in places with high potential, called Zone 1 areas, should be built with radon-resistant features, but the techniques can work anywhere. Also contact your state radon office to learn if radon-resistant features are recommended or required in your area. You can also review the states and jurisdictions that require these techniques at the EPA website.
If you are planning any major structural renovation, such as converting an unfinished basement into a living space, it is important to test the area for radon before you begin. If your test results indicate a problem, radon-resistant techniques can be inexpensively included as part of the renovation. Because major renovations can change the level of radon in any home, always test again after work is completed.
Relatively simple and inexpensive, to implement, these steps reduce radon levels, lower concentrations of other soil gases, and decrease moisture problems. In addition, they make a home more energy efficient and, on average, can reduce energy costs by $65a year.
Adding a fan to mitigate radon is relatively inexpensive in a home with an existing vent system. If the entire system has to be added after the building is completed, the costs will be much higher. The average cost to install radon-resistant features in an existing home is $800 to $2,500. The average cost to install radon-resistant features in a new home during construction is $350 to $500 (a 128 percent to 400 percent saving).
Talk to your builder about installing a radon-reduction system during major renovations or new construction. Radon-resistant features can be easily and inexpensively installed with common building practices and materials. Many builders already incorporate some of these steps in the construction of their houses to control moisture or increase energy efficiency, using either their own crews or a radon contractor. To find out about builders in your location, use the EPA Directory.
Yes. Every new home should be tested for radon within the first year even if it has radon-resistant features. Look for test kits at your local hardware store, county health department, or county extension office. You can also purchase short- and long-term test kits at www.sosradon.org. If you need more information on radon-resistant, new construction features, visit the EPA Radon-Resistant New Construction (RRNC) website or contact the National Radon Hotline at 1-800-767-7236.
For details on national radon standards, or standards for new homes in your area, visit the websites of the organizations listed below. State and jurisdiction requirements are also listed on the EPA Radon-Resistant New Construction (RRNC) website.
No. Estimates of radon concentrations in new buildings cannot be predicted by testing radon concentrations in the soil of the construction site, and such testing is a waste of resources. To prepare for potential radon concentrations and the need for mitigation, evidence suggests that it would be more beneficial to consult the EPA National Radon Potential Map, review radon measurements in nearby existing buildings prior to their mitigation, and be aware of the local jurisdiction’s code requirements for radon-resistant new construction, represented by appendix F of the IRC.
Radon Testing During Real Estate Transactions
The EPA’s “Home Buyer’s and Seller’s Guide to Radon” details several aspects related to radon testing during real estate transactions, including information on radon, the protocols for radon testing during real estate transactions, and guidance on how to interpret your radon test results.
The EPA recommends that all houses, regardless of what radon zone the house is located in, be tested for radon as part of the real estate transaction. Most often, the potential buyer requests that a radon test be done as part of the overall home inspection. This test is generally a separate service and must be requested. If the result is 4 pCi/L or greater, the EPA recommends that the potential buyer negotiate with the seller to have a radon mitigation system installed with the stated goal of bringing the radon level in the home below 4 pCi/L.
I'm selling a house. Should I have it tested for radon?
Most if not all states require that a radon test result be disclosed on the whole house disclosure, which the seller completes with the realtor. If you choose to do the test and the result is less than 4 pCi/L, potential buyers may still request an additional radon test as part of their home inspection. If the result is 4 pCi/L or greater, the issue will need to be addressed in the real estate transaction. A buyer might want to have a confirmatory test conducted. With an average radon level of 4 pCi/L or greater, it is recommended that a radon mitigation system be installed to decrease the level of radon prior to placing the house on the market.
Yes. Radon levels in a home, under typical operating conditions, will commonly reach a steady state with mild fluctuations about 12 hours after the house is closed up. Vacant houses will experience factors that may drive radon levels to lower or higher than normal averages, but the effect cannot be predicted. If the house is opened up for ventilation purposes prior to the test, it should then be closed up and a test started no sooner than 12 hours later. If short-term radon testing is being used, then the house has to be kept closed except for normal entry and exit, as if it were the winter heating season. It is recommended that the home’s heating and cooling system be operated normally for the season. If the average indoor level is 4 pCi/L, then it is expected that the radon level will be near to that average after 12 hours of a house being closed.
No. Radon can almost always be reduced in a home. Many times post-mitigation tests results are in the range of 1-3. A level of 2 would be a very good result in a home that had a mitigation system installed to reduce much higher concentrations. As long as the issue is resolved in the real estate transaction, the radon level should not be a deterrent to buying any home. When the starting concentration is 2 to 4, it is not likely that a radon contractor would guarantee any mitigation to lower the level under typical conditions for a set price.
Mitigating Radon Problems
A radon mitigation system is any system or steps designed to reduce radon concentrations in the indoor air of a building.
The EPA recommends that you take action to reduce your home's indoor radon level if your radon test result is 4 pCi/L or higher.
Radon-reduction systems work. In most new homes, use of radon-resistant features will keep radon levels below 2 pCi/L. Some radon-reduction systems can reduce radon levels in your home by up to 99 percent.
Homeowners should consider correcting a radon problem before making final preparations to sell a home. This often provides more time to address the problem and find the most cost-effective solution. In addition, they too, and not just the new occupants, will then reap the benefit of reduced risk.
The design of your house will affect the kind of radon-reduction system that will work best. Houses are generally categorized according to their foundation design — for example, basement, slab-on-grade (concrete poured at ground level), or crawlspace (a shallow unfinished space under the first floor). Some houses feature more than one foundation design. For instance, it is common to have a basement under part of the house and a slab-on-grade or crawlspace under the rest of the house. In these situations, a combination of techniques may be needed to reduce radon levels to below 4 pCi/L.
There are several methods that a contractor can use to lower radon levels in your home. Some techniques prevent radon from entering your home, while others reduce radon levels after it has entered. The EPA generally recommends methods that prevent the entry of radon.
In many cases, simple systems using underground pipes and an exhaust fan may be used to reduce radon. Such systems are called "sub-slab depressurization" and do not require major changes to your home. These systems remove radon gas from below the concrete floor and the foundation before it can enter the home. Similar systems can also be installed in houses with crawlspaces. Whether these systems are right for your home will depend on its design, as well as other factors. As mention, radon contractors have several options to choose from in selecting the best method for your home. Sealing cracks and other openings in the floors and walls is a basic part of most approaches to radon reduction. Sealing does two things: it limits the flow of radon into your home, and it reduces the loss of conditioned air, thereby making other radon reduction techniques more effective and cost-efficient. The EPA recommends against the use of sealing alone to reduce radon. By itself, sealing has not been shown to lower radon levels significantly or consistently, in part, because entry points are difficult to identify and permanently seal. Normal settling of your house will create new entry routes and reopen the old ones.
Any information that you have about the construction of your house could help your contractor choose the best mitigation system. To design the system, the contractor will start by making a visual inspection of your house.. If this inspection fails to provide enough information, the contractor will need to perform diagnostic tests to help develop the best radon reduction system for your home. The need for diagnostic tests will be determined by details specific to your house, such as the foundation design and what kind of material is under your house, as well as by the contractor's experience with similar houses and similar radon test results.
The cost of making repairs to reduce radon is influenced by several factors, including the size and design of your home. Most homes can be fixed for about the same cost as other common home repairs, like painting or having a new hot water heater installed. The average cost for a contractor to lower radon levels in a home is around $1,200, although this can range from $500 to about $2,500. Your costs may vary, depending on the specifics of your home and which radon reduction methods are needed.
Lowering high radon levels requires technical knowledge and special skills. You should use a contractor who is trained to fix radon problems.
The EPA stopped operating its National Radon Proficiency Program (RPP) on October 1, 1998. Designed to test radon contractors and provide a measure of quality control, RPP is now privately run. See the EPA's website regarding RPP for information on how to identify qualified contractors.
Many states certify or license radon contractors. Call your state radon office for information about qualified service providers in your state.
If you plan to fix the problem in your home yourself, first contact your state radon office for the EPA's technical guide, "Radon Reduction Techniques for Detached Houses."
Most radon reduction systems include a monitor that will alert you if the system needs servicing. However, you not wait for an alert to test your home. To be sure that radon levels have been reduced, you should test your home within the first month but no sooner than 24 hours after activation of the mitigation system. Potential conflict of interest can be avoided by using an independent tester, rather than having the contractor who installed the system test the radon level or doing it yourself.
In addition, it's a good idea to retest your home periodically to be sure that radon levels remain low. Testing should be done at least every two years, or as required or recommended by state or local authority. Retesting is also recommended if the building undergoes significant alteration.
There are some federal programs that might be used to help fund radon reduction in homes that are affordable to limited income families. These programs generally give money to local agencies or groups, which then fund the work. Some examples are:
- Community Development Block Grant (CDBG) Program—This funds rehabilitation and repair of affordable housing. For more information, call the U.S. Department of Housing and Urban Development (HUD) at (202) 708-3587.
- "203k" Program—This funds rehabilitation and repair of single family homes. For more information, call HUD at (202) 708-2121.
- Environmental Justice Grants—This program funds community-based organizations and tribal governments addressing environmental concerns of people of color and low income communities. For more information, call the EPA's Office of Environmental Justice at (800) 962-6215.
Some states have governmental programs that can provide loans for radon-reduction work in limited income housing. Some community groups are raising funds from private companies and foundations to pay for radon reduction in limited income homes.
To find out more about federal and state programs, or about how community groups have developed local projects to fix radon problems, contact your state radon office.
Radon in Water
When the ground produces radon, it can dissolve and accumulate in underground water sources (called ground water). When water containing radon is run for showering, washing dishes, cooking, and other uses, radon gas escapes into the air.Some radon also stays in the water.
Radon can be a concern if your drinking water comes from a well that draws from an underground source, though not all water from underground sources contains radon. If you get your water from a public water system that serves 25 or more year-around residents, you will receive an annual water quality report. These water quality reports include information on what is in your water, including radon if it has been tested.
Radon from lakes, rivers, and reservoirs (called surface water) is of much less concern. Most of the radon in surface water is released from the water before it enters the distribution system.
In most cases, radon entering the home through water will be a small source of risk compared with radon entering from the soil. The EPA estimates that indoor radon levels will increase by about 1 pCi/L for every 10,000 pCi/L of radon in water. Only about 1 percent to 2 percent of indoor radon in the air comes from drinking water.
Based on a National Academy of Science report, the EPA estimates that radon in drinking water causes about 168 cancer deaths per year: 89 percent from lung cancer caused by breathing indoor air that contained radon released from water, and 11 percent from stomach cancer caused by consuming water containing radon.
While radon in water is not a problem in homes served by most public water supplies, problems have been found in well water. If you've tested the air in your home and found a radon problem, and your water comes from a well, contact a lab certified to measure radiation in water to have your water tested. Call the EPA's Safe Drinking Water Hotline, (800) 426-4791, to get information on locating a certified lab.
If you're on a public water supply and are concerned that radon may be entering your home through the water, call your public water supplier.
Because radon in indoor air is the larger health concern, the EPA recommends that you first test the air in your home for radon before testing for radon in your drinking water. The EPA and the Surgeon General recommend testing all homes for radon in indoor air (and apartments located below the third floor). The EPA recommends that you take action to reduce your home's indoor radon levels if your radon test result is 4 pCi/L or higher.
If you have tested the air in your home and found a radon problem, you may also want to find out whether your water is a concern. If you get water from a public water system, find out whether it comes from a surface (river, lake, or reservoir) or underground source.
If the water comes from a surface-water source, most radon in the water will be released into the air before it reaches your tap. If the water comes from a ground-water source, call your water system and ask if they've tested the water for radon. If so, ask for their Consumer Confidence Report.
If you have a private well, the EPA recommends testing your water for radon. The Safe Drinking Water Hotline, (800) 426-4791, can provide phone numbers for your state laboratory certification office. You can also call the National Radon Program Services Hotline, (800) SOS-RADON, for your state radon office's phone number. Your state laboratory certification office or state radon office can direct you to laboratories that are able to test your drinking water for radon.
Estimate how much the radon in your water is elevating your indoor radon level by subtracting 1 pCi/L from your indoor air radon level for every 10,000 pCi/L of radon that was found in your water. (For example: if you have 30,000 pCi/L of radon in your water, then 3 pCi/L of your indoor measurement may have come from radon in water.) If most of the radon is not coming from your water, fix your house first and then retest your indoor air to make sure that the source of elevated radon was not your private well. If a large contribution of the radon in your house is from your water, you may want to consider installing a special water treatment system to remove radon. The EPA recommends installing a water treatment system only when there is a proven radon problem in your water supply.
Currently, there is no federally-enforced drinking water standard for radon.
The EPA does not regulate private wells, but it is proposing to regulate radon in drinking water from community water suppliers (water systems that serve 25 or more year-round residents). The EPA proposed the rule in October 1999 and plans to finalize it in August 2000.
The EPA is proposing two options.
The first option would require community water suppliers to provide water with radon levels no higher than 4,000 pCi/L. Because about 1/10,000th of radon in water transfers to air, this would contribute about 0.4 pCi/L of radon to the air in a home. This level will be permitted if the state also takes action to reduce radon levels in indoor air by developing the EPA-approved, enhanced state radon in indoor air programs (called Multimedia Mitigation Programs). This is important because most of the radon you breathe comes from soil under the house. This option gives states the flexibility to focus on the greatest problems, encouraging the public to fix their homes to reduce radon in indoor air and to build homes that keep radon from entering.
A second option is provided for states that choose not to develop enhanced indoor air programs. Community water systems in those states will be required to reduce radon levels in drinking water to 300 pCi/L. This amount of radon in water contributes about 0.03 pCi/L of radon to the air in your home.
Even if a state does not develop an enhanced indoor air program, water systems may choose to develop their own local indoor radon program. This will require them to meet a radon standard for drinking water of 4,000 pCi/L. This option enables overall risks from exposure to radon, both through air and water, to be reduced.
Radon can be removed from water by using one of two methods: aeration treatment, or granular activated carbon (GAC) treatment.
Aeration treatments involve moving bubbling air through the water, which helps to strip radon from the water. An exhaust fan is used to vent the radon outdoors.
GAC treatment filters water through carbon. Radon attaches to the carbon ,leaving the water free of radon. GAC filters tend to cost less than aeration devices. However, radioactivity collects on the filter, which may cause a handling hazard and require special disposal methods for the filter.
For more information on aerators and GAC filters, contact NSF International, at (800) 673-8010, and the Water Quality Association, at (630) 505-0160. These are both independent, nonprofit organizations.
In either treatment, it is important to treat the water where it enters your home (using a point-of-entry device) so that all the water will be treated. Point-of-use devices, such as those installed on a tap or under the sink, will only treat a small portion of your water and are not effective in reducing radon.
It is important to maintain home water treatment units because failure to do so can lead to other water contamination problems. Some homeowners opt for a service contract from the installer to provide carbon replacement and general system maintenance.
*Source: National Radon Program Services