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Reducing Radon Levels
For radon reduction work, you should always consider the use of contractors who are
certified (and trained) in a Radon Proficiency Program. We maintain a list
of contractors who are certified for radon mitigation by the National
Environmental Health Association, www.neha.org,
(exit DHS) or the National Radon Safety Board, www.nrsb.org.(exit
DHS) For independent consulting on radon mitigation, call one of the Wisconsin
Radon Information Centers toll free at 888 569-7236 (888 LOW-RADON)
Sealing: Virtually all radon in Wisconsin comes from the soil
beneath houses. Radon at 300 to 1,000 pCi/L or more is in the gasses in the soil
under basement floors everywhere. Gaps and openings to soil through basement floors and
walls should be sealed with gas-tight materials. The caulk type with the best adhesion to
concrete is polyurethane (not silicone). However, experience by researchers has shown that
sealing cracks and openings in basements will result in reductions of radon by more than
50% in only about 20% of the houses in which it is applied. Since it can be
inexpensive and is part of the next method, it is worth a try, but one shouldn't expect it
will necessarily have a major effect. It might reduce radon levels significantly if the
area of openings that are sealed adds up to several square inches. Hairline cracks are not
worth sealing.
Soil Depressurization is usually highly effective, reducing radon
to below 2
pCi/L. Air is withdrawn from beneath the basement floor with a
continuously-running fan in a 3 or 4-inch diameter pipe which exhausts at roof level. This
reduces the air pressure below the floor, so air in the basement flows down to the
depressurized zone, through small cracks and openings that could not be sealed, instead of
soil gases containing radon flowing up into the basement through those openings.
The State of Wisconsin has distributed to
all public libraries in Wisconsin copies of an eleven-minute videotape, Radon Reduction:
Sub-Slab Depressurization, showing a system installed and how it works.
A brief animated video
(requiring Shockwave) (exit DHS) is at the State of Pennsylvania's radon
website. Some radon mitigation supply
sources have pictures at their sites.
The cost
for a proficiency-listed contractor to install a system is usually around $1,200, and can
range from $800 to $2,000. Sub-slab depressurization is not a do-it-yourself project
unless you have considerable contractor skills.
For more information on reducing radon, consult the Radon Information Centers,
and with Certified Radon Mitigation Contractors.
Radon Mitigation System
Checklist
To verify that a soil depressurization radon control system meets EPA
standards, see the second page of the checklist
(PDF, 43 kb) (exit
DHS) that has been developed by the American Society of Home Inspectors in conjunction
with the U.S. EPA.
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