How to Read Your Radon Test Result

Your radon test came back with a number followed by pCi/L. Here’s what that number means and what to do about it.

What pCi/L means

pCi/L stands for picocuries per liter of air, a measure of how much radioactivity from radon is in the air you breathe. Some labs and digital monitors also show Bq/m³ (becquerels per cubic meter). To convert, 1 pCi/L equals 37 Bq/m³, so 4 pCi/L is about 148 Bq/m³.

The EPA’s guidelines

Result	What the EPA recommends
4 pCi/L or higher	Fix the home
2 to 4 pCi/L	Consider fixing
Under 2 pCi/L	No action needed; retest every couple of years and after renovations

There’s no level of radon that’s completely safe; the guidelines are about where fixing makes the most sense.

What to do next

If your short-term test was 4 pCi/L or higher

Do a second test to confirm before paying for a system. If you’re not in a hurry, a long-term test (90 days or more) gives the best picture of your average. If the first result was very high, or you’re in a home sale, a second short-term test is fine. If the two results average 4 or more, plan for mitigation.

If it was between 2 and 4

A long-term test will tell you where you really are, since radon rises and falls with weather and season. Many homeowners in this range still choose to fix.

If it was under 2

Good news. Retest every couple of years, and after big changes like finishing the basement, new windows or a new heating system.

Why results vary

• Radon is usually higher in winter, when houses are closed up.
• Storms and wind change air pressure and can raise or lower short-term readings.
• Test placement matters. See how to do a DIY radon test right.

Already have a system?

Retest after installation to confirm it works, then every couple of years. Most systems have a gauge on the pipe; if it reads zero, the fan may have stopped.

Want a professional test or a quote for a system? See the cost guide.