Similar sort of thing in most offices, regular weekly fire alarm tests.
Then one week in the office I worked in when I was with BT, they decided to have an unannounced fire drill at that time. Then they complained it took around 3 minutes longer than usual to evacuate the building.
Many years ago l worked for a company that made and installed fire protection equipment including alarms. 30 of us in a hotel conference room gabbing on about fires and what not and the fire alarm goes off.
A brief pause...... and ......we just sat there staring at one another.
It was a false alarm as it happens. Which is just as well.