I worked at an office connected to a factory and it was not unusual to have to vacate the premises a half dozen times a year. Always a false alarm but never do to a person activating it. Better safe than sorry. The fire department was required to verify before employees could be let back in.

This was in rural Chicago suburbs. My advice to you is to always grab your car keys so you can go sit in the car. Ideally you should grab your coat unless it's hot and possibly your umbrella, too. But if you have your car keys it doesn't really matter how hot or cold it is...