Wow, so many awesome responses. I’m no dummy but I’d be afraid I couldn’t solve enough puzzles to get out, lol.
On the website of the place we went to, in their FAQ, they do ask what happens if one does not succeed. In fact, where we played, they have cameras in all the rooms so if anything happens, we can wave to it. Also, after our expired time, someone came and met us where we were, and explained how to finish the last puzzles, which we did, and the door opened to let us out. I guess it is good to know, in case someone is a little claustrophobic!