Burning with the Fire of Exactly One Sun

What exactly /is/ the point of a fire alarm? It's loud, it's annoying, it's generally ignored. The alarm went off today, and as I made my way out of the building, I glanced around quickly to make sure I wasn't simply hearing a ringing in my ears again. The quick glancing didn't really help much. People kept chatting, eating breakfast, working on their computers, or even playing pool, but nobody was headed for the door. So what is the point of the fire alarm?

As I walked down the parking lot to the gathering area, I saw a couple of trucks filled with supplies being unloaded. I passed, and I couldn't help but overhear their conversation. "That's a pretty loud alarm, huh?" "Yup. Oh well, got to get this stuff inside so I can unload at the next place." So I wasn't just hearing things, unless I was projecting very well. They heard it too, but were willing to brave the flaming inferno that was supposed to be our building simply to get their job done on time? What is the point of fire alarms?

Sure, it was just a drill or test or a bug in the system. By the time I made it to the end of the parking lot, the alarm silenced and I could again head back inside. A few other people were incapable to handling the piercing noise, apparently, as there was a bit of a crowd to get back into the one nearest door. But the majority of the population had not heeded the warning. They had stayed chained to their desks, hoping to get one more minute of work done before the ceiling came crashing in on them. For without heeding the alarm's warning, that's the risk they found themselves taking. And if the fire alarm isn't going to be heeded, what's the point of having one?

What does it take to get people to evacuate a building? An alarm isn't enough, but will smoke do? Does the smoke have to be of sufficient quantity? Or do people need to actually see a flame before they flee? How much fire? Just a tiny one, or does it have to be a blazing inferno? Does the building have to be falling down, does the electricity have to be gone? Or do they simply have to start calling it a 'doughnut alarm', and serve baked goods outside any time there's a fire?

Would they then have to start catering baked goods every day, just in case?

It turns out, though, that there was a point to the fire alarm. Without it, I wouldn't have been able to bring myself to use the "Emergency Exit Only" door situated right by my desk. And it's been calling my name for a while now, mocking me with images of bright, sun shining days.