What is a radon test?

The simplest version is a small passive detector, which measures indoor radon inexpensively and simply. Whatever the device, it should come from a qualified laboratory, and as new devices appear, your state radon office has the most up-to-date information on them.

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Test	How long it runs	What it is for
Short-term test	Stays in the home from 2 to 90 days, depending on the device, and for a minimum of 48 hours.	A faster screening result. Because radon levels vary from day to day and season to season, it is less likely than a long-term test to tell you the year-round average.
Long-term test	Stays in the home for more than 90 days.	It is more likely than a short-term test to tell you the home's year-round average radon level.
Continuous monitor	Logs readings for the whole test, run as a short-term or a long-term test under the same durations in EPA guidance.	Logs a graph over time, so you can see trends and spot anomalies rather than a single number.

The same device families come in two lengths. Short-term tests measure for 2 to 90 days, depending on the device; long-term tests find the average over more than 90 days. Charcoal canisters, alpha track, electret ion chamber, continuous monitor and charcoal liquid scintillation detectors are the usual short-term devices, and alpha track and electret detectors the usual long-term ones. Every test should run at least 48 hours, and some devices, such as a 7-day charcoal canister, need longer.

Both lengths exist because radon moves around. Rain or snow, barometric pressure and other influences make levels vary from month to month and day to day. A long-term result is more likely to show the year-round average, and a measurement of at least three months is the better estimate of a home's annual mean. See how long a radon test takes.

1. 1

   The device

   A passive detector in a sealed package, or a powered monitor if a professional tests.

2. 2

   Instructions

   Where to place it and for how long; leave it in place as long as the package says.

3. 3

   A laboratory address

   The kit tells you where to send the device; reseal the package and send it right away.

4. 4

   A result

   It comes back within a few weeks, as a radon concentration in picocuries per liter of air (pCi/L).

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2 pCi/L

4 pCi/L

00 Bq/m³274 Bq/m³4148 Bq/m³6222 Bq/m³8296 Bq/m³10+370 Bq/m³

• Below 2 pCi/L (below 74 Bq/m³)Below both of EPA's guidance levels.
• 2 to 4 pCi/L (74 Bq/m³ to 148 Bq/m³)EPA recommends considering a fix when the level is between 2 and 4 pCi/L.
• At or above 4 pCi/L (148 Bq/m³ and up)EPA recommends fixing a home when the radon level is 4 pCi/L or higher.

EPA recommends fixing a home when the radon level is 4 pCi/L or higher. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. What a given number means is covered in how to read a radon test.

You can run a radon test yourself or hire a qualified tester, very often a home inspector, who chooses a device to suit the situation. Qualified testers may use any of the passive devices as well as active monitors, and a qualified tester is the recommended route when buying or selling a home.

Either way, a test is the only way to know whether you and your family are at risk, because radon levels can vary greatly from home to home. More on the choice is in can I test for radon myself.