This might be useless trivia but I found it interesting. It turns out that while you are sleeping your brain stops responding to odor stimulation. Researchers exposed sleepers to really intense and noxious smells and that did not awaken any participants in the deepest stage of sleep. It turns out that we "wake up and smell the coffee," not the other way around. Alternatively, if your spouse passes gas in the middle of the night, it won't be the odor that awakens you it will be the sound.
Science Daily May 19, 2004