How Is Radon Measured? How does an Airthings Instrument Measure Radon?

“New” air fills the sensor in about 30-45 minutes. The sensor itself counts events continuously and it keeps a ledger or these counts on an hourly basis. In order to calculate the actual radon concentration, there is quite some math involved but the bottom line is that a new calculation is run every hour and involves the counts for the past 24 hours. So every hour there is a new update to a 24-hours average.

In practical terms, this means that if you had an abrupt change of radon concentration from - say - zero to 1000 (and held it there), the expected reading would be a rising concentration level over 24 hours until it reaches the new steady state. The 30 minutes of diffusion time in the sensor is negligible in this scenario.

There are some details in this description that we are omitting here: the statistical nature of the detection of the alpha decay that adds a random component to the radon count and the way the app presents the data which introduces another level of averaging depending on the time window the user is looking at in the plots.

That being said, the response time is fairly well suited for the typical natural dynamic of radon concentration in a household environment as long as the sensor is kept in the same position.

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