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 monitor whether installing the mitigation system has 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.
- Blue vertical lines in the plot indicate reboots when the long term averaging was cleared.
- The red vertical bar marks the installation date of the sub-membrane depressurisation system.
- Horizontal green lines are results from commercial alpha-track and charcoal lab tests.
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.
- WHO Handbook on Indoor Radon
- US EPA Mitigation Standards
- The data logger uses an Arduino-based controller board to read the LED display on the electronic radon monitor. I am too lazy to write it up in great detail, but Chris Nafis has provided a very good write up of how he built his which is essentially the same. The main differences are that I use EmonCMS for data logging and Flot for the plots.
If you have comments or suggestions feel free to contact me:
2017-02-24 11:32 PM