Ask A Scientist General Science Archive

name         Richard Wells
status       other
age          60s

Question -   We are buying a home in Doe Run, Missouri for retirement. The
realtor called us today and said that a test for Radon GAs showed 5.8 ersus
a acceptable reading of 4.0. What is normal and what would be the remedy?
The realtor says a ventilation system will aleviate the problem and the
seller will give me the money as a credit to fix it.
Does this sound OK? Or, are they just pulling a fast one on this guy from
California, not used to basements, and not used to testing a house for
RADON!
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You can find the answer(s) to your inquiry from the E.P.A. website:
http://www.epa.gov/iaq/radon/pubs/

However, I am not qualified to make specific recommendations regarding
whether/how to make the level of radon "acceptable".

Vince Calder
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Richard,

No, they're not pulling a fast one -- based on what you have presented in
your question. Do an Internet search on the word "radon" -- looking for
testing and mitigation -- and you'll find much useful information on the
radon problem.

Assuming you received a valid test -- and the level really was 5.8 pCi/L as
opposed to the EPA action level of 4.0 pCi/L, the EPA recommends that the
home be mitigated to a level as far below 4.0 pCi/L as possible. However,
you should be aware that weather can affect test results. Your result is so
close to the action level, that it cannot be said with certainty that the
home has a radon problem. Of course, a valid short-term test result of 10.0
pCi/L is an almost certain indication that radon is present in unacceptable
amounts.

The best kind of test is a long-term assessment that takes approximately one
year -- testing through all four seasons. Such a test averages out seasonal
and weather influences that can influence a short-term rest result.
Obviously, the time-frame of a real estate transaction cannot tolerate a
long-term test protocol. Thus we are stuck with a short-term test and the
uncertainties attendant to it.

Making the best of an uncertain situation, I suggest you have the home
tested again -- if time permits. If the result is above 4.0 pCi/L again, you
can be more sure that mitigation is in order.

The mitigator will install a sub-slab depressurization system (SSD). In
short, the air will be power-vented from under the basement floor. This
almost always fixes the problem. AND it enhances the re-sale potential of
the property as it provides your family with a much-improved indoor air
situation. By the way, a reputable mitigator will guarantee that the home
will test below 4.0 pCi/L after the SSD system is installed.

Regards,
ProfHoff 380
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The sellers sound on the up-and-up.  The chronic exposure limit to airborne
radon is 4 picocuries per liter.  Your 5.8 isn't far above that, so it won't
be hard to get your new house within limits.  Radon is created by decay of
naturally-occurring radium, which in turn comes from uranium-bearing rocks.
That's why some areas have more radon problems than others: the local
bedrock contains differing levels of uranium.

Radon generated in bedrock diffuses into a house's basement.  Radon is
heavier than air, so it tends to stay in the basement, and in fact to settle
in the sump.  When we bought our house in Illinois, its basement also had
above-limit radon levels (I believe it was 6 pCi/L).  The seller had to put
in a mitigation  system (basically a fan to pump air from the sump to the
outside of the house).  It'll be less hassle for you to just have the
realtor arrange for a contractor to do the work.  The realtor should know
the local businesses better than you.

Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois
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