--- title: "Short-Term vs. Long-Term Radon Tests: Which Do You Need?" canonical: "https://radonmitigationyorkpa.net/radon-guide/short-term-vs-long-term-radon-test/" pubDate: "2026-10-01T00:00:00.000Z" updatedDate: "2026-10-03T00:18:00.000Z" author: Radon Mitigation York PA description: Short-term radon tests give a fast answer in 2 to 90 days. Long-term tests show your true yearly average. Learn which fits a home sale or your own home. --- # Short-Term vs. Long-Term Radon Tests: Which Do You Need? Choose a short-term [radon test for your home](/services/radon-testing/) when you need a quick answer, such as during a home sale or for a first screening. Choose a long-term test when you want the truest picture of your average year-round exposure. Short-term tests run 2 to 90 days. Long-term tests run more than 90 days. Many homeowners use both. ## What counts as short-term and long-term? The [EPA's Citizen's Guide to Radon](https://www.epa.gov/sites/default/files/2016-12/documents/2016_a_citizens_guide_to_radon.pdf) splits radon tests into two groups by length: - **Short-term tests** stay in your home for 2 to 90 days. Most run 2 to 7 days. - **Long-term tests** stay in your home for more than 90 days. The length matters because radon levels change from day to day and season to season. A longer test averages out more of those swings. ## Short-term radon tests ### Common devices - **Continuous radon monitors.** Electronic devices that log readings every hour. Professionals use these for home sales. - **Charcoal canisters and pouches.** Low-cost kits that absorb radon and go to a lab. - **Electret ion chambers.** Devices that measure radon by the drop in an electric charge. Some are set up for short tests, some for long tests. ### Pros - Fast results, often within days - Fits the short inspection window in a home sale - Low cost for a first screening - A professional continuous monitor shows hour-by-hour data ### Cons - Captures only a few days, which may run higher or lower than your yearly average - Requires closed-house conditions, starting 12 hours before tests under four days - More sensitive to weather, such as storms and high winds ## Long-term radon tests ### Common devices - **Alpha track detectors.** A small plastic film records tracks left by alpha particles. The lab counts them after the test. - **Long-term electrets.** Electret devices set up for longer periods. ### Pros - Closest to your real year-round average exposure - Averages out weather swings and seasonal changes - No strict closed-house rules; you live normally with windows as usual - Low cost for the amount of data ### Cons - Takes at least three months to get a result - Not practical for a home sale - Gives one average number, with no hourly detail ## Side-by-side comparison | Factor | Short-term test | Long-term test | |---|---|---| | Length | 2 to 90 days | More than 90 days | | Closed-house conditions | Required for tests under 4 days | Not required | | Best for | Home sales, fast decisions, first screening | True yearly average | | Weather effects | Higher | Lower | | Results | Days | Months | ## Which test should you choose? ### You are buying or selling a home Use a short-term test. A professional continuous monitor running at least 48 hours is the usual choice for real estate in Pennsylvania. It gives a fast answer, hourly data and a report from a DEP-certified tester. ### You want a first check of your own home A short-term kit is a fine place to start. If the result is below 2 pCi/L, your risk is lower. If it is between 2 and 4 pCi/L, think about a long-term follow-up. If it is 4.0 or higher, follow up soon. ### Your first short-term result was high The EPA lays out two paths for follow-up: - **Follow up with a long-term test** if your first result was close to 4 pCi/L and you want the truest answer. Fix the home if the long-term average is 4 pCi/L or more. - **Follow up with a second short-term test** if your first result was well above 4, or you want an answer sooner. Fix the home if the average of the two short-term tests is 4 pCi/L or more. The higher the first result, the more sense it makes to move quickly. A very high result is not one to wait three months on. ### You want to track a mitigation system over time After a system is installed, a short-term clearance test confirms it works. A long-term test later can show how it holds up across seasons. The EPA recommends retesting a mitigated home every two years. ## How season affects each test A short-term test captures the conditions of one week. In a York winter, the house is sealed and the furnace is running, which can push results up. A summer test with frequent door traffic may read lower. A long-term test smooths those changes out. That is part of why the two types can disagree. Learn more about the [best time of year to test for radon](/radon-guide/best-time-to-test-for-radon/) and how season affects a single test. ## York context York County is in EPA Radon Zone 1, the highest potential category, and PA DEP reports that about 40% of homes tested in Pennsylvania come back above 4.0 pCi/L. In an area like this, many homeowners start with a short-term test for speed, then use a long-term test to confirm a borderline number. ## Key takeaways - Short-term tests run 2 to 90 days; long-term tests run more than 90 days. - Short-term tests are best for home sales and quick decisions. - Long-term tests give the truest year-round average. - If a first short-term result is 4.0 or higher, follow up with either test type, based on how high it was and how fast you need an answer. - Short-term tests need closed-house conditions; long-term tests do not. ## Frequently Asked Questions ### Is a long-term test more accurate? It is more representative of your yearly average, because it covers more weather and seasons. A short-term test can be just as precise for the days it covers. ### Can I run both at the same time? Yes. Some homeowners run a short-term test for a quick answer while a long-term test runs in the background. ### Which test do mitigation companies use after a system install? A short-term clearance test, run no sooner than 24 hours after the system starts and within 30 days, per EPA guidance. ## Book a certified short-term test If you need a fast, reliable answer, schedule radon testing in York, PA with a professional continuous monitor. Call [(717) 356-3035](tel:+17173563035) any time for a same-day callback.