Use metal dryer ducts to help prevent dryer fires. Consumer Reports says that flexible dryer ducts made of foil or plastic are the most problematic because they can sag and let lint build up at low points. Ridges can also trap lint. Metal ducts, either flexible or solid, are far safer because they don’t sag, so lint is less likely to build up. In addition, if a fire does start, a metal duct is more likely to contain it. See our dryer venting safety report for more tips as well as photos and a dryer-venting video