Radon in Maryland Homes: What Every Baltimore Buyer Needs to Know

Radon is colorless, odorless, and radioactive — and it’s the second leading cause of lung cancer in the United States. If you’re buying or selling a home in the Baltimore area, radon testing isn’t optional. It’s essential.

What Is Radon and Where Does It Come From?

Radon is a naturally occurring gas produced by the decay of uranium in soil and rock. It seeps up through the ground and enters homes through foundation cracks, floor drains, sump pits, and gaps around utility penetrations. Once inside a closed home, it accumulates — especially in basements and lower floors.

Maryland is a moderate-to-high radon risk state. The EPA and the state of Maryland both recommend testing all homes regardless of location. That said, certain areas — particularly those with older housing stock in Baltimore City and County — show elevated radon levels at higher rates than the national average.

What Level Is Dangerous?

Radon is measured in picocuries per liter (pCi/L). The EPA action level is 4.0 pCi/L — if your test comes back at or above this number, mitigation is recommended. The national average indoor radon level is 1.3 pCi/L. The average outdoor level is about 0.4 pCi/L.

It’s worth noting that the EPA also recommends considering mitigation for levels between 2 and 4 pCi/L, especially in homes where occupants spend significant time in lower levels. There is no known safe level of radon exposure.

How Is Radon Testing Done?

Short-term tests typically run 48 to 96 hours using a charcoal canister or electronic monitor placed in the lowest livable area of the home. The test device is then sent to a certified lab for analysis. During testing, windows and doors must remain closed (closed-house conditions) to ensure an accurate reading.

Long-term tests run for 90 days or more and give a more accurate picture of average annual exposure. For real estate transactions, short-term tests are standard.

At Precision Home Inspection, we use calibrated electronic continuous monitors that provide an hour-by-hour readout of radon levels throughout the test period. This gives you significantly more data than a simple charcoal canister — including graphs showing if radon levels spiked at any point during the test.

What If the Test Comes Back High?

Elevated radon levels are fixable. The standard mitigation approach is a sub-slab depressurization (SSD) system — a pipe runs through the slab or foundation and a small fan draws radon from beneath the home and vents it harmlessly outside before it can enter the living space. Mitigation typically costs between $800 and $2,500 depending on the home’s construction and can reduce indoor radon levels by up to 99%.

In a real estate transaction, a high radon test result gives the buyer grounds to request mitigation as a condition of sale. Many sellers will either complete mitigation or offer a credit rather than lose the deal.

Should You Test Even If There’s Already a Mitigation System?

Yes — always. Existing mitigation systems can fail, lose fan pressure, or become inadequate if the home has been altered. We always test homes with existing systems to verify they’re working properly. A passing test with a system in place is actually reassuring. A failing test means the system needs service before closing.

Schedule Radon Testing in Baltimore

Precision Home Inspection provides certified radon testing throughout Baltimore City, Baltimore County, Harford County, Howard County, and surrounding areas. Testing can be added to any home inspection or scheduled as a standalone service. Results are typically available within 48–72 hours of test pickup.