Gas duster, also known as canned air, is a product used to clean electronic equipment and other sensitive devices that cannot be cleaned using water. The can comes with a straw to direct the forceful wind that it can produce. The gases inside the can have been compressed to the point that they have become liquid, and they evaporate before leaving the can since the valve draws from the top (unlike most aerosol cans which have a straw that draws from the bottom of the can). Despite the name "canned air," the cans actually contain gases that are much easier to compress into liquids, such as difluoroethane, trifluoroethane, or tetrafluoroethane. Hydrocarbons, like butane, were often used in the past, but their flammability forced manufacturers to use fluorocarbons.