Model 951 | Why does the nukeALERT "recalibrate" as I travel around ?

When the nukeALERT is turned on, it calibrates itself to the natural radiation background.  When the nukeALERT notices the background has reduced, it will recalibrate itself to improve the sensitivity.  When you are travelling, your device may detect a lower natural background environment and recalibrates itself to ensure maximum detector sensitivity.  You often see a reduced background count and a recalibration if you take the nukeALERT into a car or truck, for example.