How can a clean fridge harbor a bad smell?

Sometimes smells stick around a lot longer than we would all like. Try this: Put vanilla extract on a saucer, put it on a shelf and let the fridge run empty with the saucer inside for a couple of days. Bowls with coffee grounds, activated charcoal or cat litter also work. If none of these methods work, then the odor has probably penetrated the insulation and needs to be replaced.