In EPA’s Buyer/Sellers Guide you are instructed to mitigate if your results are over 4 picoCuries per liter. In the Citizen’s Guide you are advised to conduct a follow-up test, if the results are above 4, to confirm the first test results.

EPA does say that if the results are close to 4, (i.e. 4.1), that there is a 50% chance that the actual level is, “somewhat below, or above 4pCi/L.” (From my reading the, “somewhat”, is close to 25%)

If short term results are over 10 picoCuries per liter you should plan to mitigate. Less than 10 picoCuries I would want to see some long term data. I would really like to see long term data, period.

Short term testing can be affected by environmental factors such as wind, rain, stormy weather, and frontal passages. Testing under these conditions should not be used unless the results are low. All these environmental factors are “worst case” conditions and can cause elevated levels of radon in the home

FAQs

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What is radon?

Radon is a colorless, odorless, and tasteless gas.  It is a result of decaying uranium.

Why has radon become such an issue lately?

Radon has always been around as a naturally occurring gas in the environment. However, as home building standards improved and homes became much more efficient and tightly sealed, there were less ways for gases to escape a home.  Older homes with drafts allow gases to escape.  So new homes must be "mitigated" to provide an escape route for those gases.

Who should worry about radon?

The surgeon general has warned that radon is harmful.  Smokers are especially vulnerable.

Where is radon?

Radon is mostly found in areas with a lot of granite and rock.  However, that doesn't mean that your area can be ruled out if your home isn't near a lot of rock.  One home in a neighborhood could have radon and the home beside it could not.  So just because your neighbors have received low radon readings doesn't mean that you should not also get tested.

My test results were right around 4.0.  Do I still have to mitigate?

Many people may receive results that are just above the EPA's limit of 4.0 and feel that they are "close enough" and therefore don't have to pay to mitigate. You do have choices:

 - Conduct a long term test.  Environmental circumstances during the time period of your test could affect the results.  Things like rain, snow, ice or a simple front moving through the area could impact your results.  A long term (minimum 90 days) test can provide a more accurate result.

What is wrong with short term testing?

Radon fluctuates daily and seasonally. For this reason, radon measurements should be taken for at least a month for a short-term test. Short-term test results will usual be within a factor of 3 of the long-term average. So if you get a short-term
result of 3 pCi/L, you can expect your long-term radon to be within the range
from 1 to 9 pCi/L.

Problems occur when the results are at or very near to the action level of 4 picoCurries per liter. 

Football Analogy

“... So, they stretch out that chain, and if it's VERY close the referees may look at the chain and the ball for several seconds before making the call, one way or the other. But, it's a clear-cut call.”

”Now, let's suppose that the length of the ball is not constant, but instead fluctuates randomly, within limits, but let's say that about every tenth of a second it randomly gets a little longer or a little shorter, let's say a maximum of about 6 inches longer and 6 inches shorter than a normal football. Also, let's suppose that the length of the chain is also not constant but shrinks and stretches, within limits, but in a random manner, let's say a maximum of 3 inches shorter and 3 inches longer than the standard 10 yards. How is the referee going to make a determination? Part of the time, it's a first down, part of the time it is not.”

”This is pretty much what radon testers are faced with when making a measurement that is very close to 4 pCi/L. The decay of the radon in the air is a random process. The measurement of the radon, by whatever method, is a random process.”