What is the accuracy of the radon sensor?
The accuracy of a radon sensor refers to how close its readings are to the true value of the radon concentration in the environment being measured. In the case of our radon sensor, the accuracy is specified as :
σ for 7-Day average: ± 10% at ~200 Bq/m3 or ~5.4 pCi/L after 30 days of continuous measuring
σ for long term average : +/-5% at ~200 Bq/m3 or ~5.4 pCi/L after two months of continuous measuring
So what is the accuracy at radon levels below 200 Bq/m3 or 5.4 pCi/L?
The photo above shows two radon sensors side by side that are under 5.4 pCi/L. The average of the two monitors is 4.2 pCi/L ((4.56+3.83)/2). ± 10% of 4.2 pCi/L is 4.62 pCi/L and 3.78 pCi/L. So even though these two monitors are below our accuracy statement level, they are still within 10% of one another.
A good way to picture measuring low levels of radon is to think of our radon sensor as a bucket that is collecting rainwater. If it is raining heavily, the bucket will fill up faster and we can get a good estimate of the amount of rainfall in a shorter amount of time and more accurately. Similarly, when the radon levels are high, the radon sensor collects more alpha particles, allowing it to calculate radon measurements more accurately. However, just like with rainfall, it's still important to collect data over a longer period of time to get a more accurate and representative measurement. The hourly sample from the monitor can be thought of to be emptying the bucket every hour to assess the average rainfall.
As the radon concentration in the environment being measured decreases below 200 Bq/m3 or 5.4 pCi/L, the standard deviation of the sensor may decrease. This is because at lower concentrations, the amount of radiation emitted by the radon gas is also lower and as a result, there is less radiation available for the sensor to detect. At lower levels, any fluctuations or errors in the sensor's measurement become more significant relative to the small amount of radiation being detected.
In other words, at lower radon concentrations, the signal-to-noise ratio of the sensor decreases, meaning that the strength of the signal (the radiation emitted by the radon gas) becomes weaker relative to the amount of noise (random fluctuations or errors in the sensor's measurement). This can make it more difficult for the sensor to accurately measure the radon concentration in the environment being measured.
Based on the above information, it is important to note that the accuracy of the radon sensor may vary depending on the radon concentration in the environment being measured. If the radon concentration is below 200 Bq/m3 or 5.4 pCi/L, the standard deviation, and the readings may not be as reliable as they would be at higher concentrations.
With all of that being said, are you ready to start comparing your monitors? Please follow the steps below :
Be sure to start measurement segments for the two or monitors at the same time.
Place the monitors in the same location and exposed to same conditions. (For example, be sure that they are in same room, right beside each other, and away from any direct sources of ventilation.)
Be sure to let the monitors measure for at least 30 days. (Measurements will continue to get closer to one another the longer the monitors run side by side).
Please note: This increase in standard deviation with low radon levels is not specific to Airthings, rather it is the unavailable standard across all consumer-grade radon sensors.