Testing
Radon Testing: How to Get a Result You Can Act On
Testing is the only way to know a building's radon level. The quality of the decision that follows depends on how the test was conducted — duration, placement and building conditions all shape the number on the report.
Why homes are tested
Radon cannot be seen or smelled, and it varies from building to building even on the same street. Homes are commonly tested when they are bought or sold, after a renovation that changes the foundation or ventilation, when a neighbor's result prompts curiosity, or simply because a level has never been measured.
Homes with mitigation systems are also tested — periodically, and after any work that affects the system.
Testing before mitigation
A mitigation decision starts from a measurement. Beyond the number itself, the test tells a professional something about the building: which level was measured, under what conditions, and whether the reading is consistent with the construction they observe on site.
That is why keeping the original report matters — it becomes part of the project record.
Short-term and long-term measurement
| Measurement type | What it captures | Typical use |
|---|---|---|
| Short-term test | A snapshot of a limited period, sensitive to weather and how the building was operated during the test. | Fast answers, including transaction timelines; often followed by a confirming measurement. |
| Long-term test | A longer averaging period, generally more representative of the year-round average. | Understanding what a home you own is typically exposed to. |
Proper testing conditions
- Follow the closed-building conditions described in the device instructions and published guidance.
- Keep windows and exterior doors closed except for normal entry and exit.
- Avoid running window fans, whole-house fans or other equipment that changes building pressure.
- Do not disturb, move or cover the device during the test.
- Note the start and end times exactly as the instructions require.
- Return the device to the laboratory promptly when required.
Where the device goes
Guidance focuses on the lowest level of the home that is lived in — or that could reasonably be lived in — because that is where occupants are exposed. Placement details such as distance from exterior walls, floors and vents come from the device instructions and published protocol, and they are not arbitrary.
A device placed in a closet, on the floor, near a heat source, or beside a draft is measuring something other than the room.
Interference to watch for
- Windows opened during the test, including briefly for ventilation.
- Severe weather or high winds during a short-term measurement.
- HVAC changes, dehumidifiers or fans that alter building pressure.
- Construction or renovation work opening the foundation.
- Devices moved between rooms mid-test.
- Delays returning a laboratory device after the exposure period.
Understanding your result
Once you have a number, the question becomes what published guidance recommends for that level, and whether the test conditions make the number reliable.
Already have a test result? Understand it and see the next steps.
When a certified testing professional helps
Hiring a certified tester is common where the result carries consequences — a real-estate transaction, a disputed reading, a building with unusual construction, or a multifamily or commercial property. In Pennsylvania, persons and firms performing radon testing for others are generally required to hold DEP certification, subject to applicable exemptions.
Need a certified tester or a mitigation quote?
Share your test result, foundation type and project details. We pass your request to independent radon professionals — we do not perform the work ourselves.