I was in the commercial fire alarm system field and worked in the Raleigh area for a year, here's my thought.

If the alarms were sounding that long in a new building, their MAY have been an inspection. Their also MAY have been signs announcing this fact.
For airline personnel to ignore an active fire alarm usually means they know why and are not concerned.

The order to evacuate over speakers is commonly an automatic part of the system. You get strobes and a loud multi-pitched tone, followed by a recorded announcement to evacuate, followed by the tones again. Repeat as programmed.

Their are specific decible requirements and the only way to check different areas during an inspection is to just let the horns go while you walk around with a decible meter.
I know from experience Raleigh has some of the strictest inspections I've been involved with.

I've never done it in an airport, but I know when I accidentally tripped a system in a shopping mall, it was turned off in a few minutes and then mall security came over.
( I was working on an individual department store system that I had turned silent. Their was a mall system detector thisclose to the entrance of where I was. Ooops.)