Radon gas:
Heath Hazard with a Simple Solution
By Greg Pohlman, Complete Home Inspection Services, LLC
Radon gas, what is it?
Radon gas is a radioactive gas that comes from natural deposits of uranium
in the soil. Odorless, tasteless, and invisible, radon is a byproduct
of decaying uranium. It seeps up into homes and buildings and enters the
air we breathe. Radon may also be emitted from building materials such
as granite counter tops and stonework around fireplaces; however, the
major source for radon in Colorado is the soil beneath our homes, schools
and businesses. Radon enters through cracks in solid floors, construction
joints, cracks in walls, gaps in suspended floors, gaps around service
pipes, cavities inside walls and through the water supply.
The EPA action level for radon is 4.0 pCi/L (picocuries per liter). The
EPA recommends homes be mitigated if the average radon level is 4.0 pCi/L
or greater. The average outdoor radon level is .4 pCi/L. The national
average indoor radon level is 1.3 pCi/L. Surveys conducted by the Colorado
Department of Public Health and Environment indicate that four out of
ten homes in Colorado have levels that exceed 4.0 pCi/L. 1
Radon can be a problem in homes of all types: old homes, new homes, drafty
homes, well insulated homes, homes with a basement, or homes with properly
ventilated crawl spaces. Radon levels can vary from one house to another
depending on the concentration of uranium in the soil beneath. Your home
may have an average radon level of less than 4.0 pCi/L, while your neighbor's
home could have an average radon level well in excess of 4.0 pCi/L.
Next to lung cancer caused by smoking, Radon is the second leading cause
of lung cancer in the United States. The EPA estimates radon causes approximately
20,000 deaths in the U.S. each year.
Radon gas is considered a Group A carcinogen, which means it is known
to cause cancer in humans with prolonged exposure. Radon is an unstable
atom and will break down into radon decay products. Since radon gas is
in the air, radon decay products formed will also be in the air. Radon
decay products are electro statically charged. When you inhale you breathe
in both radon gas and radon decay products. The radon gas is exhaled and
the radon decay products stick to the tissue inside your lungs. Before
your lungs can clear the radon decay products, they can further break
down and irradiate the lung tissue. It is the radon decay products that
actually present the health risk associated with radon gas. 2
What if I find a home I want to purchase and it has a radon problem?
The EPA recommends that you know what the indoor radon level is in any
home you consider buying. Ask the seller for their radon test results.
If the home has a radon-reduction system, ask the seller for information
they have about the system. If the home has not yet been tested, you should
have it tested.
"If you like a home, buy it-the radon problem can
be fixed."
Once the house is tested and discovered to have unacceptable levels of
radon, contact a Certified Radon Mitigation Contractor to discuss installing
a radon reduction system. Radon mitigation contractors that have gone
through the National Environmental Health Association National Radon Proficiency
Program can be found online at www.radongas.org. The EPA and the Surgeon
General recommend testing all homes below the third floor for radon. The
EPA also recommends testing in schools.
Two ways to test your home for radon
Short term testing is done in your home for two to ninety days depending
on the device. Short term test devices such as charcoal canisters, alpha
track, continuous monitors, electret ion chambers, and charcoal liquid
scintillation detectors are the most common. They are easy to use. Just
follow the directions on the box.
Long term testing takes ninety-one to 360 days during normal living conditions,
meaning that windows can be opened, air conditioning can be operated,
etc. Test devices used for long term testing include alpha track or electret
detectors. Long term testing will give you a better idea of your year-round
exposure to radon. 3
In Steamboat Springs, short term radon test kits can be obtained free
(if still available) at the CSU Extension Office in the Routt County Annex
Building and at local hardware stores. Both long and short term test kits
are available online at; www.radon.com.
New homes can be built with radon-resistant features
Radon-resistant techniques (features) may vary for different foundations
and site requirements. If you're having a house built, ask your builder
if they're using EPA's recommended approach (International Residential
Code, Appendix F, or ASTM E 1465-08). If your new house was built (or
will be built) to be radon-resistant, it should include these
basic elements: 
- A. Gas Permeable Layer
A four-inch layer of clean gravel is placed beneath the slab or flooring system to allow the soil gas to move freely underneath the house. This gas-permeable layer is used only in homes with basement and slab-on-grade foundations; it is not used in homes with crawlspace foundations. - B. Plastic Sheeting
Plastic sheeting with seams sealed is placed on top of the gas permeable layer and under 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 below-grade openings in the concrete foundation floor are to be sealed with polyurethane caulking to reduce soil gas entry into the home. - D. Vent Pipe
A three or four-inch gas-tight or PVC pipe (or other gas-tight pipe) 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 included in the attic to make the wiring and installation of a future vent fan easier. A separate breaker is placed in the electric panel to power the vent fan. An alarm or system indicator installed along the vent fan indicates when the vent fan is not operating properly. 4
- Most Common Radon Mitigation Techniques - Basic Principles and Design
- Sub Slab Depressurization (SSD)
In a home constructed with a basement on a concrete slab, a hole is drilled through the concrete slab through which a four-inch PVC pipe is connected and routed to the exterior of the home. An inline turbo fan is attached to the piping; exhaust piping is routed vertically along the exterior of the house to the roof line to safely exhaust radon gases.
(Piping connected to hole in slab; fan attached to piping on exterior) - Sub Membrane Depressurization (SMD)
Sub Membrane Depressurization is employed when your home has a crawl space and typically costs more to install since more materials and labor are needed. A perforated plastic pipe is laid on the soil in the crawl space. Next, a plastic radon barrier is placed over the piping and soil and sealed at the seams and around the interior of the foundation, concrete pads, posts, water lines, etc. A fan connected to the perforated piping draws radon from beneath the plastic and exhausts it harmlessly outdoors.
(Radon barrier covering soil & perforated piping in crawl space; fan attached on exterior) - Sump Pit Depressurization
An existing sump pit can also be used for collection and removal of radon gases. A sealed cover can be installed over the sump pit in such a manner that piping is routed to the exterior where a fan removes radon gases. Sump pump discharge piping and electrical cords that exit the cover must have an airtight seal.
(Sump pit connection; system indicator & power converter) - Perimeter Drainage System
A radon reduction system may also be employed by connecting to an existing perimeter drainage system on the exterior of the foundation. A fan can be connected to a cleanout pipe on the exterior of the foundation. The daylight drain pipe is fitted with a special one-way flapper valve that allows drainage when water is flowing, but otherwise closes off the pipe to allow a proper vacuum. One way drain valves must also be installed in garage floor drains or basement floor drains connected to the perimeter drain pipe.
(Fan is connected to perimeter drain pipe; one-way valve installed on day light drain)
Requirements for radon systems to meet EPA's Radon Mitigation Standards
- The discharge point of the radon system can contain very elevated levels of radon. To avoid exposure to occupants and neighbors, the discharge of the pipe must be
- At least ten feet above grade
- At least ten feet away from any opening which is two feet below discharge
- Above or at eave of roof
- Fans should not be located inside the home or in a crawl space. They can be located in an attic, outdoors, or in a garage, provided there is no living space above the garage.
- There should be an indicator in a prominent location that will easily indicate to the occupant if the system is functioning properly.
- Power to the fan should be in accordance with local building codes, including permits where required.
- All portions of the system are to be labeled and a simple instructions manual with warranties provided to the homeowner.
- All homes with radon mitigation systems should be retested no sooner than twenty-four hours (not later than thirty days) after installation to verify adequate reduction in radon levels. The home should also be retested every two years.2
You may find out more information on radon gas on the EPA's website at; www.epa.gov/radon.
1 EPA's website, www.epa.gov/radon.
2 Colorado Department of Public Health and Environment, "Dealing with Radon in Realestate Transactions", revised 2004.
3 EPA, "A Citizens Guide to Radon".
4 EPA, "Home Buyers and Sellers Guide to Radon".
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