My very first beer was a strong old ale that clogged up the airlock and exploded. It exploded in the morning, and I was sleeping, but my wife heard it. She said it shook the house and was very loud. For some reason, though, when she looked in the basement and didn't see anything unusual (it was tucked away in a hidden corner), she just shrugged it off. I didn't find out until about 5 pm. We have natural gas, so I was shocked that she hadn't said anything. Lesson learned!