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A can of Dust-Off brand gas duster

Another brand of gas duster

Gas duster (also erroneously referred to as canned air) is a product consisting of liquified difluoroethane, trifluoroethane, or tetrafluoroethane in a spray can, with a long nozzle that enables the user to direct a precisely focused blast of gas. Gas dusters do not use compressed air, but other inert gases that are much easier to compress into a liquid state. Hydrocarbons, like butane, were often used in the past, but their flammability forced manufacturers to use fluorocarbons.

A gas duster is usually used to clean or dust delicate or sensitive items such as electronic components and computer equipment, as the gases used do not leave residues on sensitive equipment nor do they create static. The spray can often reach places where other cleaning implements cannot.

When the can is held upright and activated, gas flows out through the nozzle. The pressure inside the can therefore drops, and is no longer sufficient to keep the contents as a liquid; so some of the liquid boils, until the equilibrium pressure is re-established. The vaporization of a liquid is endothermic, so heat is absorbed, and the can becomes cold.

If the can is held upside down, then its contents are expelled as a liquid. This liquid evaporates very quickly at standard temperature and pressure, chilling anything in contact with it. This process can produce very cold temperatures, easily sufficient to cause frostbite. Similar cans with dip tubes are marketed as "freeze spray," and will expel liquid when held right side up.

Since gas dusters are one of the many inhalants that can be easily abused, many manufacturers have added a bittering agent to deter people from inhaling the product. Recently, in the United States and Canada, some Office Max, Office Depot, Staples and RadioShack stores have begun to ask for ID to verify if the customer is 18 years or older.

• Dust-Off: a brand of gas duster

• Alliance for Consumer Education
• Snopes: Adolescents huffing from cans of Dust-Off brand compressed air have died.