Thanks for taking the time to type that all out, Jesselp. As an ex-Manhattanite, I can appreciate what you went through. Except for not grabbing your gear, which was right there, on your way out, sounds like you acted rationally and appropriately to keep yourself safe.

JohnN already beat me to the point, but there's one aspect of office life that really keeps you away from gear at your desk--meetings. Many people spend the majority of their time running from meeting room to meeting room. Many of these meeting rooms could be on a different floor from their desk. So I think it pays to keep some things on you, unless you work in a very small office and you're generally very close to your supplies throughout the day.

I'm rather surprised that you basically had the stairwell all to yourself. You'd think that more people who prefer the stairs, but I guess I'm wrong. Either that, or else you guys reacted faster than most people and just beat the rush.

I'm also one who would disagree with the suggestion that the elevators should've been locked down. High-rise office buildings are not designed to quickly evacuate the entire building population through stairs alone, even in case of fire. If there is no fire or other immediate danger to the building itself or imminent risk of losing power, using elevators can greatly speed up the evacuation of a building. Of course, every situation is unique. But like thseng seemed to allude to, I wonder if the building staff might've jumped the gun on the evacuation order, though. In general, you're generally safer indoors unless your own building is on fire or contaminated somehow. If all I had to act on was hearing some boom or rumble outside, I think I would personally prefer to stay indoors until I had more information. Of course, in your case, you were instructed to leave, so that's a different situation.

In your case, you were probably in greatest danger from getting run over by a distracted driver who was looking at the steam plume or gawking at all the people trying to get away! Half joking, but half serious, too.