A build up of sewer gases in your home doesn't just create a foul odor reminiscent of a hot-summer-day cow pasture. Inhaling the methane that is contained in it (itself an odorless gas) can also lead to headaches, difficulty concentrating, and heart palpitations. What's worse: if enough methane accumulates in your home, the simple flicker of a pilot light can cause it to ignite. If you smell sewage, check your bathroom vent pipe (or "stink pipe") and make sure it doesn't have any holes or loose connections. And no, using duct tape and a terrycloth towel to seal it, like this homeowner did, is not the way to go.