A dust spray can often be used as a freeze spray. Many gas dusters contain HFC-134a (tetrafluoroethane), which is widely used as a propellant and refrigerant. HFC-134a sold for those purposes is often sold at a higher price, which has led to the practice of using gas dusters as a less expensive source of HFCs for those purposes. Adapters have been built for such purposes, although in most cases, the use of such adapters will void the warranty on the equipment they are used with. One example of this practice is the case of airsoft gas guns, which use HFC-134a as the compressed gas. Several vendors sell "duster adapters" for use with airsoft guns, though it is necessary to add a lubricant when using gas dusters to power airsoft guns. Health and safety 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. Some U.S. states, as well as the UK, have made laws regarding the abuse of gas duster, as well as other inhalants, by criminalizing inhalant abuse or making the sale of gas duster and other inhalants illegal to those under 18. Because of the generic name "canned air", it is mistakenly believed that the can only contains normal air or contains a less harmful substance (such as nitrous oxide, for example). However, the gases actually used are denser than air, such as difluoroethane. When inhaled, the gas displaces the oxygen in the lungs and removes carbon dioxide from the blood, which can cause the user to suffer from hypoxia. Contrary to popular belief, the majority of the psychoactive effects of these inhalants is not a result of oxygen deprivation. The euphoric feeling produced stems from cellular mechanisms that are dependent on the molecular structure of the specific inhalant, as is the case with all psychoactive drugs. Their exact mechanisms of action have not been well elucidated, but it is hypothesized that they have much in common with that of alcohol. This type of inhalant abuse can cause a plethora of negative effects including brain and nerve damage, paralysis, serious injury, or death. Since gas dusters are often contained in pressure vessels, they are considered explosively volatile. Environmental impacts Global warming Difluoroethane (HFC-152a), trifluoroethane (HFC-143a), and completely non-flammable tetrafluoroethane (HFC-134a) are potent greenhouse gases. According to the Intergovernmental Panel on