I was off last week, and it was the week we moved into new office space. Mid morning yesterday, the fire alarm (which I discovered is directly above my head) went off and nobody moved. The person next to me mentioned they were still working on them, the painters were setting them off, they were told to ignore them, if there was an issue they would get an announcement after the alarm.

My point is they knew that history and I did not, it could be the same at the airport. The alarm could be going off every hour or two, and the people were told they would get a notification if it was a real issue.