Which Radon Test Fits Your Situation?

Start with your situation

• I've never tested my home

  Either a short-term test (2–90 days) for a quick initial read, or a long-term test (90+ days) for a fuller year-round picture, is a reasonable starting point — both are recognized approaches. A short-term test requires closed-house conditions (below) to be accurate; a long-term one doesn't.

• I got an elevated result and want to confirm it

  A second test — especially if your first was a short-term test — adds confidence before you decide on next steps. Radon can vary with season and weather, so one reading is a data point, not a certainty. If your result was at or above 4 pCi/L, work through the confirmation sequence here; if you're still interpreting the number itself, see what your number means.

• I'm buying or selling a home

  The EPA recommends hiring a qualified, professional tester for a real-estate transaction rather than a DIY kit. In Pennsylvania, that professional is legally required to hold radon testing certification from the state DEP — more on that below.

• I recently had mitigation installed

  Pennsylvania's professional testing protocol sets a specific window for this: a post-mitigation test generally can't happen sooner than 24 hours or later than 30 days after the system is completed and turned on, and the system has to keep running the whole time you're testing. See how mitigation systems are verified after installation.

• I want a better picture of my home's level over time

  A long-term test (90+ days) is built for this — because it runs across different weather and seasons, it reflects your home's year-round average rather than one moment.

Why placement and conditions matter

A test only tells you something useful if it's done the way it's designed to be done. Pennsylvania's own regulation for certified radon testing sets specific placement rules: the device goes at least 20 inches but no more than 6 feet off the floor, at least 3 feet from exterior doors, windows, or vents, at least 1 foot from ceilings and exterior walls, at least 4 feet from heat sources, and at least 7 feet from sump pits — somewhere it won't be disturbed. CDC's general consumer guidance (about three feet off the ground) falls comfortably within that range; the two aren't in conflict, PA's rule is just more specific.

For a short-term test, closed-building conditions matter: windows stay closed, exterior doors stay closed except for normal entry and exit, and for any test under 96 hours, those conditions need to start at least 12 hours before the test begins. Normal permanently-installed heating and cooling can keep running, but whole-house fans can't operate during the test, and portable window fans need to come out or be sealed in place. Pennsylvania's rule also holds off on short tests under 96 hours during unusually severe storms or winds of 30 mph or more.

If you're using a DIY radon test kit, follow the manufacturer's instructions carefully. The Pennsylvania requirements above govern the protocol DEP-certified professionals must follow, not a legal requirement for homeowner self-testing.

Source: 25 Pa. Code § 240.310 (Testing protocols); CDC, "Testing Your Home for Radon" (cdc.gov/radon/testing), for the general consumer framing.

Testing after mitigation: Pennsylvania's specific window

If a mitigation system was just installed, Pennsylvania's certified-testing regulation sets an exact window for confirming it worked: the test generally can't start sooner than 24 hours or later than 30 days after the system is completed and turned on, and the system has to run continuously for the entire test. This is the rule certified professionals follow for a post-mitigation test specifically — not a general claim about every DIY situation. See how a mitigation system is verified after installation.

Source: 25 Pa. Code § 240.310 — "The postmitigation test may not be performed sooner than 24 hours or later than 30 days following the completion and activation of the mitigation system... The mitigation system must be operated continuously during the entire test period."