High Risk

ZIP Code 21120

Baltimore County, Maryland — Bentley Springs

Zone 1EPA Classification
>4Predicted pCi/L
33.5%Above action level
0246810
>4pCi/L
Above EPA action level

What This Means

Baltimore County, Maryland is in EPA Radon Zone 1, the highest risk category. The EPA predicts average indoor radon levels greater than 4.0 pCi/L in this area — above the EPA action level. The EPA strongly recommends testing all homes in Zone 1 areas. If your home tests above 4.0 pCi/L, a radon mitigation system can reduce levels by up to 99%.

What You Should Do

1
Test your home immediately. Purchase a short-term radon test kit ($10–$30) or hire a certified professional. Place the test on the lowest livable level of your home.
2
If your test result is 4.0 pCi/L or higher, install a radon mitigation system. A qualified radon mitigator can install an active soil depressurization system for $800–$1,500, reducing levels by up to 99%.
3
Re-test within 24 hours of installation to confirm the system is working, then test again every 2 years to ensure continued effectiveness.

EPA Zone Details

ZIP Code21120
CountyBaltimore
CityBentley Springs
StateMaryland (MD)
EPA Radon ZoneZone 1 — High
Predicted Indoor Radon>4 pCi/L

Source: EPA Map of Radon Zones

CDC Testing Data

Homes Tested158
Above 4.0 pCi/L53
% Exceeding Action Level33.5%

Source: CDC Environmental Health Tracking Network

Radon & Your Basement in Baltimore County

Baltimore County is in EPA Zone 1, the highest risk category. Basements and ground-level rooms in this area are very likely to have elevated radon concentrations. If your home has a basement, it should be your first testing location.

Radon concentrations are typically highest in the lowest level of a home. However, radon does not stay confined to the basement — it migrates to upper floors through stairways, HVAC ducts, and gaps in flooring. Even if your basement is unfinished or rarely used, elevated radon there can affect the air quality on your main living floors. Always test on the lowest livable level.

Baltimore County Radon Map

Counties colored by EPA radon zone. Red = Zone 1 (high), Orange = Zone 2 (moderate), Green = Zone 3 (low).

Check Another ZIP Code

Nearby ZIP Codes

21117 Owings Mills, MD High 21122 Riviera Beach, MD Moderate

Frequently Asked Questions

What is the radon risk level for ZIP code 21120?

ZIP code 21120 is in Baltimore County, Maryland, which is classified as EPA Radon Zone 1 (high risk). The predicted average indoor radon level is >4 pCi/L.

Should I test for radon in 21120?

Yes. The EPA recommends testing all homes for radon regardless of zone. Since 21120 is in a high-risk Zone 1 area, testing is especially important.

What county is ZIP code 21120 in?

ZIP code 21120 is in Baltimore County, Maryland (MD).

Is it safe to live in ZIP code 21120?

ZIP code 21120 is in a high-risk EPA Zone 1 area. While this does not mean every home has dangerous radon levels, the probability is elevated. The EPA strongly recommends testing all homes in this zone. With proper mitigation, homes in high-risk areas can achieve safe radon levels.

Does radon in the basement affect upper floors in Baltimore County?

Yes. Radon enters through the foundation and can migrate to upper floors through stairways, HVAC systems, and structural gaps. While concentrations are typically highest at the lowest level, upper floors in Baltimore County homes can still have measurable radon. Always test on the lowest livable floor.

How much does radon mitigation cost in Maryland?

In Maryland, radon mitigation systems typically cost between $800 and $2,500 depending on home size, foundation type, and local labor rates. The most common system (sub-slab depressurization) averages $1,000-$1,500. The fan lasts 10-15 years and costs $150-$300 to replace. Some states offer financial assistance programs for radon mitigation.