We have had a fire alarm in the building where I work today. Not a drill, an alarm. We calmly (well, mostly) put on our coats and walked to the stairwell, and then down. It was chaotic on the ground floor; people were holding exterior doors open and shouting to each other. Before I got out of the building one of the guards announced that while an alarm had been activated, it had been investigated and it was safe to return to our offices, so I got into an elevator and went back to my desk.
But the adrenaline effects are still with me: I'm a bit shaky, my stomach is full of acid and I keep needing to take a deep breath (must be hyperventilating a bit). I managed the stairs fine, even with my bugout bag (and I remembered it, go me!) but I won't be very capable of a long walk after going down the stairs--my leg muscles are very tired.
It's good practice, and I'm glad there was no fire.