Aerosol Dispenser

Aerosol Dispenser container and valve designed to dispense a wide variety of substances in the form of fine sprays, foams, or liquid streams. The product to be dispensed, such as paint, cosmetics, or food, is sealed in the container with a propellant gas under pressure.

Certain propellants such as nitrous oxide or carbon dioxide remain gaseous when pressurized in these containers. Others, such as the chlorofluorocarbons, may liquefy (see Fluorine). In a two-phase system the product mixes with the liquid propellant that expands into a gas when released and breaks the product into tiny droplets. A three-phase system consists of a layer of product between layers of nonmixing liquefied propellant at the bottom and gaseous propellant at the top. In both systems depressing the push button on the valve allows the product to be forced up a tube and through the valve. The liquefied gas in the bottom of the container vapourizes to keep the pressure constant.

Since the 1970s, chlorofluorocarbons (CFCs) have come under scrutiny as a possible threat to the atmospheric ozone layer. These propellants have been banned in Britain, the United States, and several other countries for all but essential uses (see Atmosphere; Ozone Layer).