Is radon high in ZIP 20657?

Low. The model's predicted long-term basement average for ZIP 20657 is 1.5 pCi/L (SD 0.07), with above-ground floors at 1.3 pCi/L. That is about 32% below the average US ZIP code (2.2) and close to the Calvert County average of 1.6. It ranks 9 of 12 ZIPs in the county.

Do I need to test my home in 20657?

Yes, once. Even in a low-predicted ZIP the EPA recommends every home be tested; a single house's foundation and ventilation can put it several times above its neighbors. One short-term kit answers it.

What EPA radon zone is ZIP 20657 in?

ZIP 20657 lies mostly in Calvert County, which the EPA classifies as Radon Zone 1 (highest potential (predicted average > 4 pCi/L)). Zones are county-wide and date from 1993; the ZIP-level prediction above is from a 2001-2021 model built on millions of tests.

Radon levels in ZIP 20657

LowEPA Zone 1

ZIP 20657 (Calvert County, Maryland): predicted long-term basement average of 1.5 pCi/L (model estimate), about 32% below the average US ZIP (2.2) and close to the Maryland average (1.3). This is the most populous ZIP in Calvert County.

Test ZIP 20657 once anyway - radon varies house to house

The predicted basement average here is 1.5 pCi/L, below the EPA's 2 pCi/L "consider fixing" threshold. That's good news for the area - but the EPA still recommends every home be tested, because foundation cracks, soil pockets and ventilation make one house very different from its neighbor. One inexpensive kit settles it.

Get a short-term test kit →Or track it with a continuous monitor

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Predicted (model estimate). The pCi/L figures on this page are long-term area averages from a peer-reviewed national model built on millions of real radon tests (2001-2021). They describe the typical home in this area - not your home, which can be several times higher or lower. The EPA radon zone is a separate, 1993 county-level classification. How the numbers work.

1.5 ± 0.07

pCi/L predicted basement mean (model SD)

1.3 ± 0.06

pCi/L predicted upstairs mean

1.4 ± 0.07

pCi/L predicted typical screening test

How 20657 compares

Within Calvert County, ZIP 20657 ranks #9 of 12 ZIPs by predicted basement level; the county average is 1.6 pCi/L and its ZIPs run from 1.4 to 2.2. The county is EPA Radon Zone 1. About 20,483 people lived in this ZIP at the 2010 Census.

Both basement (1.5) and upstairs (1.3) predictions are under 2 pCi/L. That is reassuring for the area, but the model's own uncertainty (± 0.07) and house-to-house variation mean a test is still the only way to know your home.

Other ZIP codes in Calvert County

206391.7
206781.6
207321.5
207361.6
207542.2
206851.7
206761.8
206881.4
206891.8
206291.4
206151.5

ZIP 20657 radon questions

Is radon high in ZIP 20657?: Low. The model's predicted long-term basement average for ZIP 20657 is 1.5 pCi/L (SD 0.07), with above-ground floors at 1.3 pCi/L. That is about 32% below the average US ZIP code (2.2) and close to the Calvert County average of 1.6. It ranks 9 of 12 ZIPs in the county.
Do I need to test my home in 20657?: Yes, once. Even in a low-predicted ZIP the EPA recommends every home be tested; a single house's foundation and ventilation can put it several times above its neighbors. One short-term kit answers it.
What EPA radon zone is ZIP 20657 in?: ZIP 20657 lies mostly in Calvert County, which the EPA classifies as Radon Zone 1 (highest potential (predicted average > 4 pCi/L)). Zones are county-wide and date from 1993; the ZIP-level prediction above is from a 2001-2021 model built on millions of tests.

ZIP pages are generated for ZIPs predicted at or above 2.5 pCi/L and for the most populous ZIP in each county; all other ZIPs appear in their county table. Methodology.