If you are a US-based Airthings customer, you may have noticed that your radon reading recently changed from Good (green) to Fair (orange), even though your actual radon level has not changed. This is expected and is the result of an update we made to the default radon thresholds for US accounts.

In August 2026 we updated the boundary between Good and Fair for US customers from 2.7 pCi/L to 2.0 pCi/L. The Poor threshold remains unchanged at 4.0 pCi/L.

If your radon level is between 2.0 and 2.7 pCi/L, your status will now show as Fair (🟡) instead of Good (🟢).

Your actual measured radon level has not changed.

We made this update so that our US thresholds are sourced entirely from the U.S. Environmental Protection Agency (EPA), the governmental reference for radon in the United States.

EPA publishes one formal action level: 4.0 pCi/L. That number has not changed and is not affected by this update. Separately, EPA also states: "Because there is no known safe level of exposure to radon, EPA also recommends that Americans consider fixing their home for radon levels between 2 pCi/L and 4 pCi/L." (source)

2.0 pCi/L is the lower edge of that advisory range. It is not a separate EPA action level, and EPA has not changed any of its guidance. Setting our Good/Fair line at 2.0 pCi/L was a decision we made so that the app's Fair band matches the full range EPA says is worth evaluating. Previously, our Good/Fair line was 2.7 pCi/L, a figure based on the World Health Organization's reference level of 100 Bq/m³, not an EPA number. That meant our two US boundaries came from two different health bodies (WHO and EPA). This update replaces the WHO-derived boundary so that both of our US boundaries (2.0 and 4.0 pCi/L) reference the same source, EPA.

No. Your radon level has not changed, and EPA's own health guidance has not changed.

A reading between 2.0 and 4.0 pCi/L, for example 2.8 pCi/L, is not flagged by EPA as unsafe or as requiring action. It falls in the range where EPA says homeowners may want to consider evaluating or reducing radon, as a precaution, since no exposure level is considered completely risk-free. It is a different, lower-urgency category than the 4.0 pCi/L action level, where EPA recommends homes be fixed.

Is 2.0 pCi/L an official EPA "action level"?
No. EPA's only published action level is 4.0 pCi/L. 2.0 pCi/L is the bottom of EPA's advisory "consider fixing" range (2.0 to 4.0 pCi/L), which we now use as our Fair band. We describe this as based on EPA guidance, not as an EPA-declared action level.

Did EPA change its radon guidance recently?
No. EPA's guidance is unchanged. This was a change we made to how the Airthings app categorizes readings, so that our US thresholds are sourced consistently from EPA instead of a mix of EPA and WHO figures.

Why wasn't 2.7 pCi/L kept, if it was already stricter than EPA's range?
2.7 pCi/L was never an EPA number. It came from the WHO reference level of 100 Bq/m³. We changed it so that the categories US customers see are drawn from EPA guidance throughout, rather than blending sources.

Where can I read the EPA language myself?
See EPA's page What is EPA's Action Level for Radon and What Does it Mean?

Yes. If you prefer different threshold values, for example to keep using 2.7 pCi/L as your personal Good/Fair line, you can customize them in the Airthings app. Go to Settings > Thresholds and adjust the values to your preference. You can also tap Reset to default at any time to return to the current US defaults (2.0 / 4.0 pCi/L). Note that the Radon Insights advice text always uses the country default (2.0 / 4.0 pCi/L) regardless of any custom thresholds you set. See our guide: How to customize thresholds.

The EPA provides detailed information on radon action levels on their website: What is EPA's Action Level for Radon?