January is Radon Action Month (RAM). January was chosen as RAM primarily because indoor radon concentrations are at their "worst case" or highest levels for the year. Radon entry into buildings is based on pressure differentials. These pressure differentials are exacerbated during the heating season due to the "stack effect". The stack effect is a scenario whereby heated air rises within a structure via thermal bypasses, which induces the structure to increase suction on the ground on which it sits. This in-turn, increases the influx of soil gas into the structure, thereby increasing airborne radon concentrations.
Testing airborne radon concentrations this time of year will generally give a "worst case" scenario for radon. Point being; if your radon testing indicates levels > 4 pCi/l, the likelihood that your annual average is going to be below 4.0 pCi/l is very good. On the other hand, if your radon levels are > 4 pCi/l, this gives indication that at the very least; further testing is warranted. Radon mitigation should never be based on one result. But the higher above 4.0 pCi/l you are, the more confident you can become that there is a problem.
There's an old saying that states; "no news is good news"...maybe it would be if something different was discovered about radon exposure that indicated it was less of a problem than originally thought. The reality; nothings changed. Radon is still recognized as the leading cause of lung cancer in non-smokers, and the second cause of lung cancer overall. It's the intangible aspect of radon that make events like RAM necessary...to remind us of the hidden danger.
The other facet of radon that is sometimes overlooked - but is still important to consider is waterborne radon. For those of us whose daily water usage is supplied from a private drinking water well, radon has a second "highway" into your home. When you test your air for radon - you should also test the water. As is the case with any water contaminant, waterborne radon levels can fluctuate. A low reading 3, 8, 11 years ago in no way assures a low reading going forward.
TEST, TEST, TEST!