Originally Posted by
Clop_Clop
Quite common for QNH to change by one, so chances are the alerting will go off a lot when it's not needed and the alerting system could be seen as a nuisance 99% of the time when it's not needed.
The OP said that a difference of ±1 hPa would not trigger an alert, so why would you expect large numbers of false alarms ?