Diagnostic Tools We Use: Radon Monitoring – GreenBuildingAdvisor

By KOHTA UENO | August 15, 2025

This blog post recounts my experience measuring radon and the efforts to remediate the elevated gas level in my own home.

Background and radon levels

This column is not intended as “Radon 101″—Martin Holladay already did a great job of that, both on Green Building Advisor (All About Radon) and in Fine Homebuilding (Radon-Mitigation Systems). The point I want to emphasize is that radon—a colorless, odorless, radioactive gas that comes out of the ground—can have significant health impacts. The current literature says that it is the second leading cause of lung cancer after smoking.

The recommended limits for radon exposure vary, but a useful summary chart is shown in Airthing’s “Radon Levels: What Do They Mean?”

---

---

The table above presents the data both in pCi/L (Picocuries per liter of air), the U.S. measurement, and Bq/m³ (Becquerels per cubic meter), the rest-of-the-world measurement. For reference, 1 pCi/L is equal to 37 Bq/m³.

The typical “action level” (i.e., “You need to fix this”) in the U.S. is 4 pCi/L, per the Environmental Protection Agency. The World Health Organization recommends 2.7 pCi/L as a limit. Airthings has written up a comprehensive survey of radon thresholds.

Short-term monitoring

I live on the top floor of a triple decker in the Boston area, and it has the classic rubble stone walls and minimal thickness slab-over-dirt in the basement. I measured radon a few times, using “puck” style detectors (e.g., First Alert Radon Gas Test Kit). You leave them in the space that you want to measure and then send them off to a lab for analysis. They provide the average radon level for the exposed period.

I did repeated measurements over a few years, under a few conditions: