I laughed at first, and wondered what they meant. It made me think of that little Cuban kid who was on a raft. (...not Alessandro Del Toro.)
I looked into it and I see that several states require it in new buildings and remodels in building codes. Many of them have links to outside air and may even have filters on the air that comes in if a building collapses around you.
Next time you see a sign like this, know what to use it for. http://en.wikipedia.org/wiki/Area_of_refuge
Why am I mentioning this now? I just watched another "Life After People" last night with Lisa and Luiz so even though the show is theoretically "After" the existence of people, it made me think about what I would do in the unlikely event of a building collapsing around me.
...and please you know if a building did collapse, I would be one of the ones to come out singing a song ready to party in the next one.