Hey Markxxx, I coincidentally have some direct experience with the elevators and fire alarm in a Sheraton. 
I was staying at the Sheraton Premiere at Tysons Corner near DC. They had a very minor kitchen fire that set off alarms throughout the hotel. The elevators all dropped to the lobby and the door opened and stayed open.
It was a real drag to walk down ~15 flights of stairs to sit in the now very crowded lobby for like 20 minutes.