Aerosol spray

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Aerosol spray

Aerosol spray is a type of dispensing system which creates an aerosol

Particulate

Particulates, alternatively referred to as particulate matter or fine particles, are tiny particles of solid or liquid suspended in a gas or liquid....
mist of liquid particles. This is used with a can or bottle

Bottle

A bottle is a container with a neck that is narrower than the body and a "mouth." Bottles are often made of glass, clay, plastic or other impervious materials, and typically used to store liquids such as water, milk, soft drinks, beer, wine, cooking oil, medicine, shampoo, ink and chemicals....
that contains a liquid under pressure. When the container's valve is opened, the liquid is forced out of a small hole and emerges as an aerosol

Particulate

Particulates, alternatively referred to as particulate matter or fine particles, are tiny particles of solid or liquid suspended in a gas or liquid....
or mist

Mist

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History

The concepts of aerosol probably goes as far back as 1790. The first aerosol spray can was invented in Oslo

Oslo

is the Capital and largest List of cities in Norway in Norway.Metropolitan Oslo or the Greater Oslo Region makes up the third largest urban area in Scandinavia after Metropolitan Stockholm and Metropolitan Copenhagen....
in 1926 by Erik Rotheim, a Norwegian

Norway

Norway , officially the Kingdom of Norway, is a constitutional monarchy in Northern Europe that occupies the western portion of the Scandinavian Peninsula....
chemical engineer. The patent was sold to a US company for 100,000 Norwegian kroner

Norwegian krone

The krone is the currency of Norway. The plural form is kroner. It is subdivided into 100 ?re . The ISO 4217 code is NOK, although the common local abbreviation is kr....
. The Norwegian Post Office celebrated the invention by issuing a stamp in 1998.

In 1939, American Julian S. Kahn received a patent for a disposable spray can, but the product remained largely undeveloped. 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. 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

Malaria

Malaria is a Vector -borne infectious disease caused by protozoan parasites. It is widespread in Tropics and subtropical regions, including parts of the Americas, Asia, and Africa....
-carrying bugs by spraying inside tents in the Pacific during World War II

World War II

World War II, or the Second World War , was a global military conflict which involved a Participants in World War II, including all of the great powers, organised into two opposing military alliances: the Allies of World War II and the Axis powers....
. 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

Robert Abplanalp

Robert Henry Abplanalp was an American inventor who invented the Aerosol spray valve, the founder of Precision Valve Corporation and a political activist....
.

Technology (aerosol propellants)

If the can were 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 would rapidly deplete. Usually the gas is the vapor

Vapor

A vapor or vapour is a substance in the gas phase at a temperature lower than its critical temperature.This means that the vapor can be condensation to a liquid or to a solid by increasing its pressure, without reducing the temperature....
of a liquid with boiling point

Boiling point

The boiling point of a liquid is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid....
slightly lower than room temperature

Room temperature

Room temperature is a common term to denote a certain temperature within enclosed space at which humans are accustomed.Room temperature is thus often indicated by general human comfort, with the common range of 10celsius to 23?C , though climate may acclimatize people to higher or lower temperatures....
. This means that inside the pressurised can, the vapor can exist in equilibrium

Thermodynamic equilibrium

In thermodynamics, a thermodynamics#Thermodynamic system is said to be in thermodynamic equilibrium when it is in thermal equilibrium, mechanical equilibrium, and chemical equilibrium....
with its bulk liquid at a pressure that is higher than atmospheric pressure

Atmospheric pressure

Atmospheric pressure is sometimes defined as the force per unit area exerted against a surface by the weight of air above that surface at any given point in the Earth's atmosphere....
(and able to expel the payload), but not dangerously high. As gas escapes, it is immediately replaced by evaporating liquid. Since the propellant exists in liquid form in the can, it should be miscible with the payload or dissolved in the payload.

Chlorofluorocarbons (CFCs) were once often used, but since the Montreal Protocol

Montreal Protocol

The Montreal Protocol on Substances That Deplete the Ozone Layer is an international treaty designed to protect the ozone layer by phasing out the production of a number of substances believed to be responsible for ozone depletion....
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

Ozone layer

The ozone layer is a layer in Earth's atmosphere which contains relatively high concentrations of ozone . This layer absorbs 93-99% of the sun's high frequency ultraviolet light, which is potentially damaging to life on earth....
. The most common replacements are mixtures of volatile hydrocarbon

Hydrocarbon

In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. With relation to chemical terminology, aromatic hydrocarbons or arenes, alkanes, alkenes and alkyne-based compounds composed entirely of carbon or hydrogen are referred to as "pure" hydrocarbons, whereas other hydrocarbons with bonded com...
s, typically propane

Propane

Propane is a three-carbon alkane, normally a gas, but compressible to a transportable liquid. It is derived from other petroleum products during oil or natural gas processing....
, n-butane

Butane

Butane, also called n-butane, is the unbranched alkane with four carbon atoms, CH3CH2CH2CH3....
and isobutane

Isobutane

Isobutane, also known as methylpropane or 2-methylpropane, is an alkane, isomeric with butane. Recent concerns with depletion of the ozone layer by freon gases have led to increased use of isobutane as a gas for refrigeration systems, especially in domestic refrigerators and freezers, and as a propellant in aerosol sprays....
. Dimethyl ether

Dimethyl ether

Dimethyl ether is the organic compound with the formula CH3OCH3. The simplest ether, it is a colourless gas that is a useful precursor to other organic compounds and an aerosol propellant....
(DME) and methyl ethyl ether are also used. All these have the disadvantage of being flammable. Nitrous oxide

Nitrous oxide

Nitrous oxide, commonly known as "laughing gas", is a chemical compound with the chemical formula Nitrogen2Oxygen. At room temperature, it is a colorless Flammability gas, with a pleasant, slightly sweet odor and taste....
and carbon dioxide

Carbon dioxide

Carbon dioxide is a chemical compound composed of two oxygen atoms covalent bond to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state....
are also used as propellants to deliver foodstuffs (for example, whipped cream

Whipped cream

Whipped cream is cream, often sweetened, whipped with air. Cream with 30% or more fat can be mixed with air, and the resulting colloid is roughly double the volume of the original cream as air bubbles are captured in a network of fat droplets....
and cooking spray

Cooking spray

Cooking spray is a spray form of various types of oils, combined with lecithin, an emulsifier, and a propellent such as food-grade alcohol, nitrous oxide, carbon dioxide or propane....
). 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.

Packaging

Modern aerosol spray products have three major parts; the can, the valve and the actuator or button. The can is most commonly lacquered tinplate

Tinplate

Tinplate is sheet carbon steel covered with a thin layer of tin. Before the advent of cheap mild steel the backing metal was wrought iron. While once more widely used, the primary use of tinplate now is the manufacture of tin cans....
(steel with a layer of tin) and may be made of 2 or 3 pieces of metal crimped together. Aluminium

Aluminium

Aluminium or aluminum is a silvery white and ductile member of the boron group of chemical elements. It has the symbol Al; its atomic number is 13....
cans are also common and are generally used for more expensive products. The valve is crimped to the rig of the can, the design of this component is important in determining the spray rate. The actuator is depressed by the user to open the valve; the shape and size of the nozzle in the actuator controls the spread of the aerosol spray.

Packaging that uses a piston barrier system is often used for highly viscous products such as post-foaming hair gels, thick creams and lotions, food spreads and industrial products and sealants. The main benefit of the piston barrier system is that is assures separation of the product from the propellant, maintaining the purity and integrity of the formulation throughout its consumer lifespan. The piston barrier system also provides a controlled and uniform product discharge rate with minimal product retention and is economical.

Another type of dispensing system is the bag-in-can system (or BOV “bag on valve”). This system separates the product from the pressurizing agent with a hermetically-sealed, multi-layered laminated pouch, which maintains complete formulation integrity so only pure product is dispensed. Among its many benefits, the bag-in-can system extends a product’s shelf life. The bag-on-valve, or ABS, is widely used by sun care marketers for its benefits: all-attitude (360-degree) dispensing, quiet and non-chilling discharge. This bag-in-can system is also used in the packaging of pharmaceutical, industrial, household, pet care and other products that require complete separation between the product and the propellant.

Health concerns

There are two main areas of health concern linked to aerosol cans:

Deliberate inhalation
Inhalant

Inhalants are a broad range of drugs in the forms of gases,aerosols, or solvents which are breathed in and absorbed through the lungs. While some inhalant drugs are used for List of medical inhalants, as in the case of nitrous oxide , this article focuses on the non-medical use of inhalants, as recreational drugs which are used for their int...
of the contents to gain a high from the propellant
The piggy-backing of more dangerous particles into the respiratory tracts