It was not until 1941 that the aerosol spray can was first put to good use by Americans Lyle Goodhue and William Sullivan, who are credited as the inventors of the modern spray can.[3] Their design of a refillable spray can dubbed the “bug bomb”, was patented in 1943, and is the ancestor of many popular commercial spray products. Pressurized by liquefied gas, which gave it propellant qualities, the small, portable can enabled soldiers to defend against malaria-carrying bugs by spraying inside tents in the Pacific during World War II.[4] In 1948, three companies were granted licenses by the United States government to manufacture aerosols. Two of the three companies still manufacture aerosols to this day, Chase Products Company and Claire Manufacturing. The "crimp-on valve", used to control the spray was developed in 1949 by Bronx machine shop proprietor Robert H. Abplanalp.[3]
[edit] Propellant
If the can was simply filled with compressed gas, either it would need to be at a dangerously high pressure, or the amount of gas in the can would be small, and it would soon run out. Hence, usually, the gas is the vapour of a liquid with boiling point slightly lower than room temperature. This means that inside the pressurised can, the vapour can exist in equilibrium with its bulk liquid at a pressure that is higher than atmospheric pressure (and able to expel the payload), but not dangerously high; yet, as gas escapes it is immediately replaced by more evaporating liquid. Since the propellant exists in liquid form in the can it is desirable that it be miscible with or dissolved in the payload.
Chlorofluorocarbons (CFCs) were once often used but since the Montreal Protocol came into force in 1989 they have been replaced, in nearly every country, due to the negative effects CFCs have on Earth's ozone layer. The most common replacements are mixtures of volatile hydrocarbons, typically propane, n-butane and isobutane. Dimethyl ether (DME) and methylethyl ether are also used. All these have the principal disadvantage of being quite flammable. Nitrous oxide and carbon dioxide are also used as propellants to deliver foodstuffs (for example, whipped cream and cooking spray). Medicinal aerosols such as asthma inhalers use hydrofluoroalkanes (HFA): either HFA 134a (1,1,1,2,-tetrafluoroethane) or HFA 227 (1,1,1,2,3,3,3-heptafluoropropane) or combinations of the two.
https://en.wikipedia.org/wiki/Aerosol_spray#Propellant
