Radon Monitoring

This page describes the radon monitor we had running in our house in Boulder, Colorado, an area known for its high radon. We also lived for a few years in the Bay Area, California and I have a separate web page for the radon monitor in that house.

At home we have two Safety Siren Pro 3 electronic radon monitors. These monitors as well as multiple activated charcoal and alpha track detectors all agreed that the radon levels were typically below the US EPA acceptable limit of 4 pC/L, but frequently around the WHO recommendation of 100 Bq/m3 (2.7 pC/L). On the basis that no radon is good radon we decided to attempt to lower the levels in our house even if it was not mandated by the US EPA.

The objective of this web page is to test whether installing the mitigation system made a significant difference. Since the house has an unfinished crawlspace, the mitigation uses a sub-membrane depressurisation system, consisting of a sealed layer of 6mil Dura-Skrim reinforced plastic membrane over the entire floor with a fan drawing air from beneath the membrane and venting through the roof.

The plot shows the logged measurements from one Safety Siren Pro 3 in my home office since Aug 2013. It produces two output values; a short term average of the past week and a long term average since the last reset.

Evidently the system works. Radon levels to the left of the red marking the installation date are highly variable. After the system installation levels are stable and consistent at just over 1pC/l. One can only presume that without the mitigation system installed the small 3pC/l spike in July 2016 would have been anoth 10pC/l event like those seen in 2014.

Though the absolute calibration of the Safety Siren Pro 3 cannot be guaranteed, I do believe it is reliable to reveal trends and alert us if there is a significant change. The manufacturer claims ±10% accuracy, but also recommends annual factory recalibration which we have not done.

Useful documents:

If you have comments or suggestions feel free to contact me:

2022-04-24 4:00 PM