This is probably the most relevant bit of info for us as the ones who know what to do- don't be silent. Lead people to safety!
Several years ago, I was working in a basement office, which just happened to be in a building housing all kinds of toxic chemicals.
One day, the power went out. It turned out to be just a hapless squirrell, but we didn't know that at the time. I had a flashlight in my briefcase (even though it was a cheap one from the dollar store with weak batteries, it later caused me to be branded as a crackpot survivalist by some of my cow-orkers). We were in a windowless basement office, so we were in utter darkness. I got out my little flashlight, and a few of my cow-orkers got out their cel phones, which gave off a little light.
Everyone was more than content to simply mill about, pondering the causes of the lights going out. But when I simply said, "I think we should evacuate the building", everyone seemed to agree that it was a good idea, and they all followed my little flashlight outside.
I suspect that part of the problem is that people might be embarassed if they take action that, in retrospect, is not necessary. So if you see a little bit of smoke, they might think it's just an itsy-bitsy fire, and they would be perceived as overreacting to go outside. In our case, it really was just a mundane power outage, and everyone reacted as though it was a mundane event.
But even though nobody took any action independently, they were quite willing to follow the directions that were offered by me. And perhaps my little AA cell flashlight from the dollar store gave me some credibility. If their action had turned out to be an embarassing over-reaction, they could have blamed it on me (as they did, to some extent, by assuming that I was a survivalist nutcase because I had a cheap flashlight in my briefcase.)
The next day, we were issued an official flashlight by the company.