The Environmental Protection Agency (EPA) recommends that you take action to reduce the amount of radon in your home if your home has a radon level of 4.0 picocuries per liter (pCi/L) or higher. To put this level into perspective, an average outdoor level of radon is between 0.3 pCi/L and 0.7 pCi/L, and an average indoor level is approximately 1.3 pCi/L.
Michigan Radon Levels
Since the late 1980s, radon tests have been taken throughout Michigan and the United States. The data was collected and compared to geological formations to generate the map below. Based on this information, about 12% of Michigan's single family, detached homes can be expected to have indoor radon levels greater than 4 pCi/L. But Zone 1 areas, including Washtenaw County, have a greater potential for elevated indoor radon levels. In some cases, more than 40% of the homes could have a radon problem. However, it is important to note that elevated radon levels have been found in homes in all three zones.
All homes should be tested for radon, regardless of zone.
Zone 1 - Highest Potential - greater than 4.0 pCi/L (red squares)
Zone 2 - Moderate Potential - 2.0 pCi/L to 4.0 pCi/L (orange squares)
Zone 3 - Low Potential - less than 2.0 pCi/L (yellow squares)
Washtenaw County Radon Levels by Zip Code, 1994-2014