Compressed gases present a variety of potential physical and chemical hazards in their storage, delivery, and use. Gases may be classified as toxic, pyrophoric, flammable, irritant, corrosive, inert, and oxidizing. Large releases of inert gases may displace air and cause asphyxiation although this is most apt to occur in confined spaces. Some compressed gases may have more than one potential hazard, for example, chlorine gas is corrosive, toxic, and oxidizing. Physical hazards may involve a sudden release of pressure which results in major damage to the facility or serious personal injury. Personal injury may also be caused by the improper handling of gas cylinders.