Of residential radon tests, and sensors

In the last blog post, I started to describe how radon comes into houses, and the radioactive decay that causes it. During the home inspection process, a radon test would place some canisters in the basement for 12, or 24 hours. These canisters are then sent away to a lab for testing, and you get a result in a day or two. The Commonwealth of Massachusetts has some information about Radon as well as specific details about testing.

Figure 1. Side-by-side comparison of two radon detectors.

These tests give you a number representing the Radon level at the time when the test was done. But radon levels change throughout the day, even after the test is done. When I saw a passive radon system in the basement, I looked into getting a digital radon meter. I purchased a couple [you can find them at your local hardware store, I found mine online] and set them up in my basement.

After 24 hours they started showing numbers, and they consistently showed different numbers! I’ve blurred the manufacturer’s name on purpose.

Within reason, I can imagine differences, but when they were consistently different, and sometimes diverging, I wasn’t sure what to do. A few days later, one of them consistently showed a reading in excess of 6 pCi/L (pico-Curies/liter) and the second stayed stubbornly below 1.75 or so. What would you do?

I purchased a third one, and I put all three through a “reset” cycle, and then tossed them into a solid lead box. And I left them there, in that box for 36 hours. When I took them out, and reviewed the readings over the past 12 hours [there’s a 24 hour period when the meters report nothing], and all three of them were different. I wasn’t comfortable with that end result. I wanted higher confidence in the readings.


The next post will cover what came next, my own radon detector.

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