scarletvw wrote:
Those cans of air are what pretty much everyone uses, when they are full they will let a little bit of the liquid out. In order to use the cans properly though they need to be perfectly upright, if you tilt it one way or the other and tip it upside down it will shoot out freezing liquid. If held upright they will generally not have any issues.

boofsterb wrote:
Gas duster, also known as canned air or compressed air, is a product used for cleaning electronic equipment and other sensitive devices that cannot be cleaned using water. 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 flammable nature forced manufacturers to use fluorocarbons.

Cleaning
A gas duster is usually used to clean or dust delicate items or to reach difficult areas. Gas dusters are particularly useful for ventilation fans and electronic heat sinks, which collect dust readily and are otherwise very difficult to clean. The gases themselves do not leave residues on sensitive equipment; however, the bitterant added to prevent abuse leaves a residue, making gas dusters an inappropriate choice for cleaning anything users will come into contact with such as keyboards. They can create static electricity[1] unless a specific ESD-safe compound is added.
The can must be held upright during use. Inverting, tilting or even shaking the can during use may result in the unevaporated liquid being forced through the nozzle instead of the gas. The liquid will boil away almost instantly outside the can, producing extreme cold in the process. In liquid form, the contents of the can will act as a solvent, causing unwanted damage to surface coatings or labels, this is generally only a problem with optical lens coatings. Side effects of the intense cold can also cause problems due to localised condensation.

When the can is 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; thus, heat is absorbed, the temperature can reach −50 °C (−58 °F), and the can becomes cold.
Continued use over a short period of time results in the reduction of the can's temperature. As the temperature drops, the vapor pressure of the liquid also drops, resulting in decreasing force of the gas at the nozzle. When the force of the ejected gas at the nozzle is insufficient to accomplish anything useful in terms of dust removal, and the temperature of the can reaches the boiling point of the liquid (which is −25 °C (−13 °F) for difluoroethane), the liquid no longer evaporates into gas in any useful quantity. The can must then return to room temperature before it will again provide sufficient gas flow. Alternating between two cans (allowing one to warm while the other is being used) is one way to work around this problem during an extensive dusting job. Warming the can with a heat source can be dangerous as the can may overheat and explode.


(I think the craziest part of compressed air is the fact that they add bitterant to prevent people from huffing the gas)