A radon result can look deceptively simple: one number followed by “pCi/L.” But when you are deciding whether to move forward with a Maryland home purchase, that number can affect negotiations, repair planning, and your family’s long-term health. Knowing how to read a radon report helps you focus on the finding that matters without jumping to conclusions.
Radon is a naturally occurring radioactive gas that moves up through soil and can enter a home through cracks, sump pits, utility openings, and other gaps in the foundation. You cannot see or smell it, and a well-maintained home can still have elevated levels. A radon report is not a pass-or-fail grade on the property. It is a record of conditions during a specific testing period and a tool for making an informed decision.
Start With the Radon Result
The most prominent number on the report is usually the average radon concentration, measured in picocuries per liter of air, or pCi/L. This is the number you will compare with Environmental Protection Agency guidance.
The EPA recommends fixing a home when the radon level is 4.0 pCi/L or higher. At that level, the usual next step is to obtain estimates from qualified radon mitigation professionals and discuss who will handle the work before settlement.
A result between 2.0 and 3.9 pCi/L is below the EPA action level, but it is not necessarily a result to ignore. The EPA advises homeowners to consider mitigation at or above 2.0 pCi/L because there is no known completely risk-free level of radon exposure. Whether to pursue mitigation in this range depends on the buyer’s comfort level, the planned use of the basement, the home’s design, and the terms of the transaction.
A result below 2.0 pCi/L is generally reassuring, but it does not mean radon is absent or that future testing will always produce the same number. Radon levels naturally change with weather, ventilation, soil conditions, and how the home is used.
How to Read a Radon Report Beyond the Average
The final average matters most, but a reliable report provides context around that result. Review the property address, test location, test dates, device type, and any quality-control details. These items help confirm that the test was performed correctly and reflects the area of the home where occupants could reasonably spend time.
Check the test location
Radon testing is usually performed in the lowest livable level of the home. In a house with a finished basement, that often means the basement. If the basement is unfinished but could be used for recreation, work, storage, or future living space, it may still be the appropriate place to test.
Do not assume a test on one floor represents every part of the home. Radon is commonly higher at lower levels, which is why location is so important. A report should identify the room or area where the device was placed and note that it was kept away from drafts, exterior doors, windows, high heat, and excessive moisture.
Review the testing period
Most real estate radon tests are short-term tests, commonly lasting 48 hours or longer. The report should show the exact start and stop time. A test that is too short, interrupted, or conducted under improper conditions may not provide a dependable result.
Short-term testing is practical during an inspection contingency because buyers need answers quickly. Its trade-off is that it captures a limited window of time. A long-term test, usually conducted for more than 90 days, gives a better picture of annual average exposure. That is often more useful for a homeowner who is not under a transaction deadline.
Look for closed-house conditions
For a short-term test, closed-house conditions are generally required before and during the testing period. Exterior windows should remain closed, except for normal entry and exit. Exterior doors should not be left open, and whole-house fans or other ventilation systems that exchange indoor and outdoor air should not be used in a way that alters the result.
The report may include a statement confirming these conditions or note whether the inspector observed any concerns. If testing conditions were not maintained, ask whether a retest is appropriate. A result is only as useful as the process used to obtain it.
Confirm the device and quality checks
Radon reports may come from a continuous radon monitor, charcoal canister, or another approved device. A continuous monitor records readings throughout the test period and may show hourly fluctuations, temperature data, motion indicators, or tamper alerts. Charcoal tests provide a result after laboratory analysis but do not offer the same hourly detail.
If a continuous monitor was used, do not be alarmed by occasional spikes in the chart. Radon rises and falls throughout the day. The reported average, along with the device’s quality-control data, is what should guide the decision. A tamper alert, power interruption, or other irregularity does not automatically mean the result is invalid, but it should be explained clearly.
What Different Radon Results Mean for a Home Purchase
A result at or above 4.0 pCi/L does not mean you should walk away from the home. Elevated radon is common, including in Maryland, and mitigation is a well-established solution. Most systems use a fan and piping to draw radon gas from beneath the foundation and vent it safely above the roofline.
For buyers, the more useful question is not simply, “Is there radon?” It is, “What is the plan to reduce it, and how will we verify that the plan worked?” Depending on the market and your contract, you may ask the seller to install a mitigation system, request a credit, negotiate the purchase price, or arrange for the work after closing.
Before agreeing to any solution, clarify the scope. A mitigation proposal may include sealing accessible openings, installing suction piping, adding a fan, and placing a warning device that confirms the fan is operating. The system design can vary based on whether the home has a slab foundation, crawlspace, sump pit, or multiple foundation sections.
If the seller completes mitigation before closing, request a post-mitigation radon test. The goal is not just installation of equipment. The goal is documented evidence that the system lowered the radon level.
Questions to Ask When the Number Is High
When a report shows 4.0 pCi/L or more, keep the conversation specific. Ask whether the test met required conditions, where the device was located, and whether the report shows any device alerts or irregularities. Then ask for a qualified mitigation contractor’s evaluation rather than relying on guesses about cost or system design.
It is also reasonable to ask whether the home has an existing radon system. Some newer homes were built with passive radon-resistant features, such as a vent pipe without a fan. A qualified professional may be able to activate or improve that system, but performance should still be verified through testing.
Do not confuse radon mitigation with a general home repair. Sealing foundation cracks alone rarely provides a reliable solution because radon can enter through many hidden pathways. Proper mitigation typically addresses the pressure beneath the home, not just visible gaps.
A Low Reading Still Deserves Practical Follow-Up
If the test result is low, keep the report with your home records. Retest after major changes that could affect airflow or the foundation, such as finishing a basement, replacing HVAC equipment, installing a sump system, or completing significant renovations. Retesting every couple of years is also a sensible habit, especially if you use lower-level rooms frequently.
A home next door can have a very different radon result. Soil conditions, construction details, drainage, and foundation openings all affect how radon enters a property. Neighborhood results can provide context, but they cannot replace testing the specific home you plan to buy or occupy.
Read the Report, Then Make a Clear Decision
A radon report should give you a clear measurement, not create unnecessary fear. The key is to verify that the test was conducted properly, compare the result with the 4.0 pCi/L EPA action level, and make any mitigation decision based on documented conditions rather than assumptions.
For buyers, a thorough inspection process creates room for calm, practical decisions. At InSpec Home Inspections Maryland, the goal is to provide clear findings you can use with your agent, seller, or contractor. Whether the number is low, moderate, or elevated, the right next step is a conversation backed by a reliable report and a plan you understand.
