Radon illustration, How Radon Enters Your Home
This illustration (click to enlarge) shows how radon enters your home. (DepositPhotos)

Danny and Joe welcome callers’ questions each week on the Today’s Homeowner Radio Show.

Here’s a question from our Dec. 21 broadcast:

Ben needs to know how to migrate radon — a colorless, odorless gas — with an air-to-air exchange system.

We tell Ben the Environmental Protection Agency says the maximum radon level is 4, before a homeowner should take steps to correct the situation, and Ben says his radon level is 7. So this is a top priority. 

An air-to-air exchange system will work to get radon out but will not prevent radon from being in his home.

Consider a radon detector if you’re concerned about poisonous gas in your home. 

Listen to the embedded audio clip above for the answer! Read the blog from the Dec. 21 show and listen to the full broadcast here.

Read the sections below to learn more about radon and how to test it in your home.

What Is Radon?

Radon is an odorless, colorless gas nine times heavier than air. Produced by the natural decay of uranium found in trace amounts within soil and rocks, it is highly radioactive, producing the same deadly alpha radiation as plutonium. This dangerous gas may be found in homes, businesses, and schools worldwide. It should be noted that one in every 15 homes has elevated radon levels, making this a common risk.

Unlike most threats, testing is the only way to detect radon gas. It is considered highly dangerous by the Environmental Protection Agency (EPA) and may be either inhaled or (in some cases) ingested. But how do you test for radon, what are the risks involved, and can you eliminate it from your home?

What Are the Health Risks?

Radon is the second leading cause of lung cancer deaths in non-smokers. Approximately 21,000 lung cancer deaths per year may be attributed to radon, of which 2,900 are non-smokers. Compare this to second-hand smoke, the third leading cause of lung cancer in general, which kills approximately 3,000 non-smokers per year. The risks are higher for children, as they have a higher respiratory rate than adults.

How Does Radon Get In My Home?

Despite being heavier than air, radon is still lighter than the ground, which produces it. Over time it seeps to the surface, where it may seep into your home through numerous small openings:

  • Construction joints
  • Cracks in walls or solid floors
  • Wall cavities
  • Any gaps where service pipes enter the home
  • Gaps found in suspended floors

Radon has also been known to contaminate groundwater and, in some circumstances, enter the home through water supplies such as wells. Finally, in rare circumstances, the building materials can give off elevated radon levels.

Real Estate Concerns

When preparing to purchase or rent a home, you can request information on radon levels, just as you would termite testing or other concerns. If you plan to sell or lease your home, it is thus advisable to test ahead of time and have a copy of the results available.

Radon Testing Options

While you can’t detect the presence of radon through sight, smell, or taste, a simple test kit or hiring a professional can reveal a problem quickly. These tests determine the quantity of radon in the air by measuring via one of two systems.

pCi/L, or picoCuries per liter, is most common in the US, while the metric measurement is in Becquerels per cubic meter (Bq/m^3). One Bq/m^3 is equal to 1/37 of a pCi/L. When testing, note which form of measurement is being used.

Due to radon being heavier than air, the lower floors of your home generally have higher concentrations than the upper floors. Radon also tends to appear in higher levels during the winter when windows are shut, reducing the amount of ventilation. Additionally, as hot air rises and escapes through your roof, the cooler air is pulled upwards, which can bring additional radon from beneath your basement.

Short-Term Tests

The quickest way to check for radon is a short-term test. Depending on the detector you choose, these take between two and 90 days but are less accurate than long-term tests. Using two short-term tests in a row can help estimate your average year-long levels under time constraints. The most common detectors are:

  • Alpha Track
  • Charcoal canisters
  • Charcoal liquid scintillation
  • Continuous monitors
  • Electret ion chamber

Long-Term Tests

Any testing device which remains in your home for more than 90 days is considered a long-term test. Because they monitor the air for longer periods of time, they give a more accurate estimate of your year-long average radon levels. Alpha Track and Electret are both commonly used for long-term testing.

Hiring a Qualified Professional

Sixteen states require professionals to have some form of registration or certification before performing radon testing. All radon credentials relating to the EPA became invalid when their Radon Proficiency Program (RPP) was discontinued in 1998 and should not be considered proof of qualification. You should check to find out what requirements your state has in place before hiring a professional tester. In addition, two privately-maintained national certification programs maintain directories of qualified radon professionals:

How To Use Test Kits

As a general rule, you should follow the instructions on your test kit. However, some additional steps can help improve the accuracy of short-term tests. The EPA has developed a method using both tests as an efficient way to catch high radon levels.


Because short-term tests cannot accurately predict the year-long fluctuations of radon in your home, a little preparation is advisable.

  1. Check the weather. A two to 3-day test should not be run if you expect a severe storm or unusually high winds.
  2. Close all outer doors and windows at least 12 hours before testing for two to 3-day tests. Keep them closed as much as possible during any short-term testing.
  3. Shut down any ventilation units that move air inside or outside. Exceptions are small exhaust fans that run for only short periods, fan components of a radon-reduction system, and HVAC units that re-circulate air.
  4. Choose a location on the lowest floor of your home that receives regular use. Furthermore, the room you place the test in should also be heavily used, although kitchens or bathrooms are poor choices.
  5. Pick a spot in the room at least 20 inches above the floor and away from drafts, external walls, heat, and humidity to avoid inaccurate readings.

The EPA’s Two-Step Method

This simple method was developed to help detect dangerous radon levels more quickly. It is especially useful if you have reason to believe your home is at high risk (such as a high result in previous tests).

Take a short-term test and check the results. You must do a follow-up test if the results are 4 pCi/L or higher.

  1. If the results are 8 pCi/L or higher, immediately take a second short-term test.
  2. If the results are below 8 pCi/L, you may choose either a short-term or long-term test as a follow-up. The higher the result of the first test, the more you should consider another short-term test.

Understanding the Results

When using two short-term tests, you should average the test results. With a long-term test, only the results of that test are necessary. A final rating of 4 pCi/L or higher indicates you should consider abatement. A 2 pCi/L or lower result is considered normal, and 1.3 pCi/L is the indoor average (the outdoor average is .8 pCi/L). Remember that the conversion ratio between pCi/L and Bq/m^3 is 1:37. As radon carries risk at any level, the lower your indoor level, the better.

Dealing with Radon

While it is currently impossible to eliminate radon levels completely, several methods exist to reduce existing radon or even lower the risk in new construction projects. You should always hire a certified professional for radon-related projects, as there is a risk of worsening the problem. Be sure to get a few quotes before choosing, and try to provide as much information as possible about your home’s construction so the contractor can pick the best solution for your home.

Many methods are available to reduce your radon levels, some of which are limited to certain types of foundations. It might also be necessary to employ a combination of methods if your home has more than one type of foundation. Older homes and houses with additions, for instance, often have a basement in one part of the foundation and a slab or crawlspace in another.

Crawlspace Homes

Submembrane suction is the most common and effective method to reduce radon in a crawlspace home. To seal the area, the contractor covers the soil floor with a high-density plastic sheet. The radon under the sheet is then vented outdoors using a fan and vent pipe.

Active crawlspace depressurization is another less-effective option. In this method, the crawlspace is sealed from the rest of the home and air is pulled out using a fan. This poses problems with some appliances and may affect the efficiency of your HVAC system, increasing utility bills.

The third method is using passive or active ventilation. Passive ventilation employs existing or additional vents to allow radon to escape. Meanwhile, active ventilation adds a fan for better air circulation. Appliances, pipes, and other objects in the crawlspace may need to be insulated, especially in colder climates. Note that your energy bills may be affected by the increased ventilation.

Homes with Basements or Slab-on-Grade Foundations

One of the first things a contractor will do is make a visual inspection to determine the best abatement method for your home. When considering a soil suction method, they may also run one or more diagnostic tests to determine soil density. This density is known as soil communication and is usually determined by using chemical smoke and a vacuum cleaner hose inserted through separate holes. By observing the behavior of the smoke, the contractor can determine air movements and how dense the underlying ground is.

There are four common methods of dealing with radon in homes that have a basement and/or slab-on-grade foundation:

  • Active Subslab Suction: Also known as sub-slab depressurization, this is the most common and successful method. The contractor inserts one or more suction pipes through the floor slab into the ground beneath and/or below the slab from outside your home. How many pipes are needed depends upon how easily air can pass through the soil or crushed rock, although one pipe is often enough. A radon vent fan is then connected to the pipes to draw out radon, creating a vacuum under the slab. This fan may be located outside or in an unconditioned attic or garage.
  • Block-Wall Suction: Used in basements that employ cinder blocks or other hollow blocks for the foundation walls, block-wall suction depressurizes the walls while removing radon. Beyond the location, this method functions like sub-slab suction, often used in conjunction.
  • Passive Subslab Suction: Less effective than the active variation, the passive method doesn’t include a fan and instead relies upon natural differences in pressure and airflow to function. It’s commonly used in radon-resistant construction methods.
  • Sump-Hole Suction: This method takes advantage of existing drain tiles or perforated pipes found in homes with sump pumps. The sump is capped and becomes the location for the radon suction pipe, pulling radon away from the home and draining water. There are also other variations of drain tile suction that function on the same principle.

Other Methods

Some methods may be used regardless of the foundation type. These methods are not always very effective on their own but prove highly beneficial as part of a combined system.

  • Foundation Sealing – This method is not recommended by the EPA as a standalone remedy, although it can boost the efficiency of other methods and reduce the loss of conditioned air. The cost of sealing your foundation may thus pay for itself over time. Note that your home will naturally continue to settle, so keeping your foundation completely free of cracks is impossible.
  • Heat Recovery Ventilator (HRV) – Also referred to as an air-to-air heat exchanger, an HRV brings outdoor air into the home while exhausting indoor air. The heat or cold of the exhaust is transferred to the intake to maintain the indoor temperature while improving ventilation. This system not only reduces radon but can remove other air pollutants as well. It can be used to ventilate part or all of your home but is most effective against radon when focused on the basement or ground floor (if you have no basement). Note that this system does require power and will thus impact your energy bills.
  • House/Room Pressurization – The effectiveness of this method depends heavily upon climate, lifestyle habits, appliances, and how your home was built. It can also lead to moisture problems and higher energy bills, so it tends to be a last resort. You must keep windows and exterior doors closed as much as possible for this method to work. The goal is to use a fan to blow air into the basement or ground floor from outside or upstairs, increasing the local pressure enough to keep radon gas from entering the home.
  • Natural Ventilation – Open windows, vents in the basement or lower floors, and other openings can help temporarily reduce radon levels. These levels return after approximately 12 hours, so this method should strictly be considered a temporary measure.

A Note on Radon-Resistant Construction Methods

Suppose you are remodeling, adding an extension, or building a new home. In that case, several construction techniques will help keep radon levels low at a lower price than adding mitigation systems down the road.

One popular example uses a four-inch thick layer of gravel topped by a six-mil polyethylene sheet to serve as both a vapor barrier and separator to keep the wet concrete of the foundation from clogging the gravel layer. A vent pipe leading from the foundation up through the roof also makes an effective passive system to which a fan may later be added if an active system’s power is required.

For more information on radon-resistant construction techniques, please refer to the EPA’s page on Builder and Contractor Resources for Radon-Resistant New Construction (RRNC)

Radon-Related Costs

As with many other home risks, the overall costs incurred from radon issues will vary greatly depending on individual circumstances. Testing yourself is inexpensive, with kits (and lab results) generally running between $15 and $35. Professional testing is more accurate but expensive, averaging between $200 and $300.

Radon mitigation also varies. For example, an average passive or active suction system will run anywhere from $550 to $2,500, with the exact cost largely dependent upon your home’s size. Meanwhile, installing a radon mitigation system costs between $750 and $3,000. Annual maintenance costs range from no cost to $700, and fan replacement will cost $250 to $300 every five years. A water radon mitigation system for groundwater runs between $1,000 and $4,500 to install, with annual maintenance being $250 or less.

Editorial Contributors
Danny Lipford

Danny Lipford


Danny Lipford is a home improvement expert and television personality who started his remodeling business, Lipford Construction, at the age of 21 in Mobile, Alabama. He gained national recognition as the host of the nationally syndicated television show, Today's Homeowner with Danny Lipford, which started as a small cable show in Mobile. Danny's expertise in home improvement has also led him to be a contributor to popular magazines and websites and the go-to source for advice on everything related to the home. He has made over 200 national television appearances and served as the home improvement expert for CBS's The Early Show and The Weather Channel for over a decade. Danny is also the founder of 3 Echoes Content Studio, TodaysHomeowner.com, and Checking In With Chelsea, a décor and lifestyle blog.

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