My rule is "When the alarms go off, I leave the building."* I'll admit that in the face of such unclear evidence of any hazard, I wondered whether this might be more of a guideline. But I figure that since I am on the top floor, any problem is almost definitely between me and the ground.** And I'd rather much leave the building unnecessarily many times than get stuck once above a small problem that becomes a large one. So I went and hung out in the parking lot with a bunch of other office workers. Not long after, a fire truck rolled in, but in a "We have to show up but we know it isn't urgent" manner.
The other people on my project team showed up, and we decided to go see the art exhibition at the Art Institute of Portland (this wasn't completely random, the son of one of our team members was graduating that day, and this was the chance for the graduating class to show off their work). A bus ride down to NW 11th & Davis later, and we were in the very crowded open house. R seemed pleased to show his graphic designs and photographs to friends of his dad (I don't know Art, but it all looked good to me). I wouldn't have minded touring the rest of the show, but everyone else wanted to return to work. By the time we arrived, everyone had gotten back into the building and there weren't any more long lines for the elevators. After that, it was pretty much like any other Friday afternoon.
* Monday morning, the department admin person sent around an email from the Building Management company, saying that if the alarm isn't sounding on the floor you're on, evacuating the building is optional.
** I've thought the open central core of this building is an excellent escape route, if for some reason all six stairwells are simultaneously unavailable (I know, doesn't seem likely). With a rope and the proper hardware, one could make an impressive James-Bond-style exit, descending down from the catwalk through the atrium. The drawback would be leaving a rope behind, and having people who aren't knowledgeable think they can slide down to safety. While this can be done, the Average Cubicle-Dweller might think they can grip the rope tightly and control their descent with their hands. This might work for a short distance, but I doubt most people have the hand strength. So they start sliding too fast, which hurts their hands, causing them to reflexively loosen their grip, and suddenly they're going MUCH faster than they intended... I've thought that one could have a picture card at the top, showing how to use one's feet as a brake, but I don't know that most people, in a situation so dire that no other escape route exists, would take the time to read instructions.