At a Westin in DC last week, the alarm went off just after 5 a.m., accompanied by a loud recorded voice instructing guests to exit the hotel. I was 9 floors up, so I started to put my shoes on ... then decided to call the guest services number before I headed out. They told me they were checking on it, but they didn't think it was an issue. So I sat there for a few minutes with the alarm blaring wondering if I should evacuate - finally, they came over the loudspeaker and said it was a false alarm. The alarm rang a few more times after that, but eventually stopped.
It was an inconvenience, but I don't blame the hotel - I would rather an alarm going off when it isn't supposed to than risk an alarm NOT going off when there is an actual emergency.