The Home Buyer’s/Seller’s Guide To Radon In Air

The following information has been organized and written to serve as a guide in order to help answer the most often asked questions; thus, moving the process of buying and selling real estate along, from start to finish, when radon gas levels are found to be elevated.

What is radon gas?

The Environmental Protection Agency (EPA) defines radon as a gaseous radioactive element having the symbol Rn.  Radon is measured in pico Curies per liter of air (pCi/L).  It is further defined as an extremely toxic, colorless gas that can be condensed to a transparent liquid and to an opaque, glowing solid.  It is derived from the radioactive decay of radium, the source of which is earth and rock beneath homes, well water, and building materials.  Further the EPA states there are no immediate symptoms of radon; however, it estimates that up to 30,000 lung cancer deaths each year can, in fact, be traced to high levels of radon exposure.  To date, the only health effect, according to the EPA, which has been definitively linked to radon exposure, is lung cancer.  It is important to know that smokers are at a higher risk of developing radon-induced lung cancer.  The EPA, to date, has not published or disclosed evidence that other respiratory diseases, such as asthma, are caused by radon exposure and maintains there is no evidence that children are at any greater risk of radon induced lung cancer than adults.  The EPA suggests action be taken when a home has radon levels that equal or exceed 4 pCi/L.

Radon is also found in water.  If your drinking water comes from a surface water source such as a river, lake, or reservoir, it is likely that any radon that might be present is released into the air before reaching your water supplier or home.

Where should radon testing be conducted and at what level is it a concern?
Radon testing should be conducted in the lowest livable area of the home. This is an area that can be made livable with little modification or where a frequent amount of time will be spent. The EPA suggests that action be taken when radon levels are 4 pCi/L (Pico Curies per liter of air) or greater.
What type of radon testing is available?

Categorically, there are two types of radon tests available…long term testing and short term testing.  A long term test, or an alpha tracking monitor, is conducted for at least one month.  However, it is generally conducted over a course of 6 to 12 months.  This testing method can be desirable to average out changes in climate, which can affect the indoor radon levels, noting cold weather can be conducive in elevating radon levels. 

A short term test lasts for a minimum of 48 hours, though it can be exposed for as long as one week, depending on the criteria set by the testing company.  There are two common types of short term tests used.  The first is an activated charcoal test.  This type of test is less expensive; however, it is more vulnerable to tampering.  The second type of test is a continuous radon monitor.  This type of test is usually more expensive, but is more tamper proof.

Both tests have been found to be accurate and strive to be less than 25% inaccurate. 

NOTE: During the process of a real estate transaction, the short term test is most common and practical due to time constraints.

What if the radon level is found to be 4 pCi/L or greater?

At the buyer’s or the seller’s discretion, a second test may be conducted in order to make certain the results are consistent, thus ensuring the accuracy of the testing.  If a second test is conducted, resulting in a greater differential from the radon level of the first test, a third test may be considered.  If the first two tests have a small differential, the correct procedure is to work off of the average of the two tests.

How does the radon enter the home?

The radon is a byproduct of radium typically found in rock and soil; therefore, it is located below the home’s floor, which sits on this soil.  When buildings generate a negative air pressure (a vacuum of air rising from the building’s lowest area upward), it is this negative air pressure that pulls the radon up from the ground.  Negative air pressure is caused by multiple factors:  heat rising within the dwelling, or mechanisms, such as a heating system, being vented to the exterior.  Indoor negative air pressure is always changing.  Due to it being predicated on exterior climatic conditions, it tends to be greater in the cold weather months resulting in higher indoor radon levels.

What is the most common method to mitigate indoor radon levels?

Sub-slab depressurization (SSD):  This method neutralizes the catalyst (negative air pressure) by means of generating a vacuum below the floor of the basement, crawl space, or slab on grade, thereby pulling the radon back into the ground.  By virtue of maintaining the vacuum, the radon stays in the ground, not in the structure.

What does an SSD system consist of?

The SSD system generally consists of cutting a 4-inch diameter hole through the concrete floor, inserting a 3-inch diameter plastic pipe, and extending the pipe to the exterior roof line with an in-line fan system attached. (Refer to the photo gallery.)

How does the SSD system work?

The in-line fan generates a vacuum within the plastic pipe that is air-tightly embedded within the floor creating the necessary vacuum to pull and keep the radon contained within its origin below the floor.  (Refer to the photo gallery.)  NOTE:  Other methods of radon mitigation are sometimes suggested depending on the specifics of the dwelling; such as older structures with stone foundations, or one which is built on a crawl space.

Where is the radon vent pipe installed and what does the completed radon system look like?

When designing a radon system, the following criteria must be met:  The PVC vent piping is usually vented to the roof line of the home.  It must be 10 feet above ground level and 24 inches above the highest window, or other such openings, i.e. chimneys.  The 24-inch height clearance can be avoided by maintaining a 10-foot clearance from the specific openings on the horizontal access. Note:  Fixed windows and doors are excluded.

The first option is to extend the basement PVC pipe out over the top of the foundation through the side of the home, usually near the back corner board, and extend it upward to the eave.  This emulates the look of a downspout.

The next option depends on the design of the home.  If the home is a multi-level structure, such as a colonial style, we can extend the PVC pipe from the basement into a series of closets stacked one on top of another into an accessible attic and out through the roof.  The first and second floor closets must be stacked one on top of the other in order to facilitate this installation.

A third option may be considered if there is an attached garage with no living space above.  The PVC pipe may be routed from the basement into the garage and exited out through the garage roof.

How do I know if the radon system is doing its job and how can I be assured it will do its job in the future?

STORCH Radon Services provides follow-up testing upon the completion of all installations.  In most situations, we will provide a life-time guarantee to keep the indoor radon level below the EPA action level of 4 pCi/L.  If guarantees are applicable, they are transferable to the new home owner.

Why should I hire STORCH Radon Services to install my radon system?

STORCH Radon Services has been successfully reducing radon levels in homes for over 31 years, and we have installed over 35,000 radon mitigation systems.  STORCH Radon Services is fully insured, Rhode Island state certified, certified through the National Radon Proficiency Program (NRPP), members of the Better Business Bureau, and provide reasonable rates.  We can be contacted at 1-800-362-6290 or at

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Concern: Homes that have additions built on/with interconnected full basements. These additions with their own full basements are usually considered to be a separate entity source of contribution toward elevated radon levels.

Solution: In some instances, one mitigation system, i.e. a single fan vented to the exterior, may generate enough vacuum below the two separated basement floors achieving a more cost-efficient solution. However, if the density of the soil below the two separate basement floors is inconsistent, i.e. one with compacted soil and the other with loose soil, it may require two separate mitigation systems. In this case, the one system would be to generate a vacuum below the area of loose soil only, providing no significant mitigation to the other.

Concern: Interconnected and open to the basement dirt floor crawl spaces

Solution: In most cases, an air-tight 6 mil. plastic membrane can be installed over the dirt floor. If this is not possible, i.e. lack of height to physically access the area, an alternate means of mitigation may be necessary. The installation of an air exchange system (Heat Recovery Ventilator) may be needed to dilute the contributing radon from this area.

Concern: Open pits and channels exposing soil below concrete floors, i.e. sump pits, which can cause radon to enter into the basement and also reduce the necessary vacuum pressure the SSD system creates to mitigate the area. This can be likened to trying to vacuum your floor with a big hole in the vacuum cleaner hose!

Solution: Install a removable air-tight cover over the sump pit floor opening, or applying an expandable foam into the drainage channels.

Typical Radon Entry Points into the House