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Aerosol spray is a type of dispensing system which creates an
aerosol An aerosol is a suspension of fine solid particles or liquid droplets in air or another gas. Aerosols can be natural or anthropogenic. Examples of natural aerosols are fog or mist, dust, forest exudates, and geyser steam. Examples of anthropogen ...
mist of liquid particles. It comprises a can or bottle that contains a payload, and a propellant under pressure. When the container's valve is opened, the payload is forced out of a small opening and emerges as an aerosol or mist.


History

The concepts of aerosol probably go as far back as 1790.Bellis, Mar
The History of Aerosol Spray Cans
/ref> The first aerosol spray can patent was granted in
Oslo Oslo ( , , or ; sma, Oslove) is the capital and most populous city of Norway. It constitutes both a county and a municipality. The municipality of Oslo had a population of in 2022, while the city's greater urban area had a population of ...
in 1927 to Erik Rotheim, a Norwegian chemical engineer,Norwegian Patent No. 46613, issued on November 23, 1926 and a United States patent was granted for the invention in 1931. — Method and Means for the Atomizing or Distribution of Liquid or Semiliquid Materials, issued April 7, 1931 The patent rights were sold to a United States company for 100,000
Norwegian krone The krone (, abbreviation: kr (also NKr for distinction); code: NOK), plural ''kroner'', is currency of the Kingdom of Norway (including Svalbard). Traditionally known as the Norwegian crown in English. It is nominally subdivided into 100 ...
r. The Norwegian Postal Service,
Posten Norge Posten Norge () is the name of the Norwegian postal service. The company, owned by the Norwegian Ministry of Transport and Communications had a monopoly until 2016 on distribution of letters weighing less than 50g throughout the country. There ...
, 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. Kahn's idea was to mix cream and a propellant from two sources to make whipped cream at home—not a true aerosol in that sense. Moreover, in 1949, he disclaimed his first four claims, which were the foundation of his following patent claims. It was not until 1941 that the aerosol spray can was first put to effective use by Americans Lyle Goodhue and William Sullivan of the
United States Bureau of Entomology and Plant Quarantine United may refer to: Places * United, Pennsylvania, an unincorporated community * United, West Virginia, an unincorporated community Arts and entertainment Films * ''United'' (2003 film), a Norwegian film * ''United'' (2011 film), a BBC Two fi ...
, who are credited as the inventors of the modern spray can. Their design of a refillable spray can, dubbed the aerosol bomb or bug bomb, is the ancestor of many commercial spray products. It was a hand-sized steel can charged with a liquefied gas under 75 pounds of pressure and a product to be expelled as a mist or a foam. A public-service patent was issued on the invention and assigned to the
Secretary of Agriculture The United States secretary of agriculture is the head of the United States Department of Agriculture. The position carries similar responsibilities to those of agriculture ministers in other governments. The department includes several organi ...
for the free use of the people of the United States. Pressurized by liquefied gas, which gave it propellant qualities, the small, portable can enabled soldiers to defend themselves against
malaria Malaria is a mosquito-borne infectious disease that affects humans and other animals. Malaria causes symptoms that typically include fever, tiredness, vomiting, and headaches. In severe cases, it can cause jaundice, seizures, coma, or death. ...
-carrying
mosquitoes Mosquitoes (or mosquitos) are members of a group of almost 3,600 species of small Diptera, flies within the family Culicidae (from the Latin ''culex'' meaning "gnat"). The word "mosquito" (formed by ''mosca'' and diminutive ''-ito'') is Spanish ...
by spraying inside
tent A tent () is a shelter consisting of sheets of fabric or other material draped over, attached to a frame of poles or a supporting rope. While smaller tents may be free-standing or attached to the ground, large tents are usually anchored using ...
s and airplanes in the
Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the contine ...
during
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
. Goodhue and Sullivan received the first Erik Rotheim Gold Medal from the Federation of European Aerosol Associations on August 28, 1970, in Oslo, Norway in recognition of their early patents and subsequent pioneering work with aerosol sprays. In 1948, three companies were granted licenses by the United States government to manufacture aerosol sprays. Two of the three companies, Chase Products Company and Claire Manufacturing, continue to manufacture aerosol sprays. The "crimp-on valve", used to control the spray in low-pressure aerosol sprays was developed in 1949 by
Bronx The Bronx () is a borough of New York City, coextensive with Bronx County, in the state of New York. It is south of Westchester County; north and east of the New York City borough of Manhattan, across the Harlem River; and north of the New Y ...
machine shop proprietor Robert H. Abplanalp. In 1974, Drs.
Frank Sherwood Rowland Frank Sherwood "Sherry" Rowland (June 28, 1927 – March 10, 2012) was an American Nobel laureate and a professor of chemistry at the University of California, Irvine. His research was on atmospheric chemistry and chemical kinetics. His best ...
and
Mario J. Molina Mario José Molina-Pasquel Henríquez (19 March 19437 October 2020), known as Mario Molina, was a Mexican chemist. He played a pivotal role in the discovery of the Antarctic ozone hole, and was a co-recipient of the 1995 Nobel Prize in Chemis ...
proposed that
chlorofluorocarbon Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are fully or partly halogenated hydrocarbons that contain carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F), produced as volatile derivatives of methane, ethane, and p ...
s, used as propellants in aerosol sprays, contributed to the depletion of Earth's
ozone layer The ozone layer or ozone shield is a region of Earth's stratosphere that absorbs most of the Sun's ultraviolet radiation. It contains a high concentration of ozone (O3) in relation to other parts of the atmosphere, although still small in rel ...
. In response to this theory, the U.S. Congress passed amendments to the Clean Air Act in 1977 authorizing the
Environmental Protection Agency A biophysical environment is a biotic and abiotic surrounding of an organism or population, and consequently includes the factors that have an influence in their survival, development, and evolution. A biophysical environment can vary in scale ...
to regulate the presence of CFCs in the atmosphere. The
United Nations Environment Programme The United Nations Environment Programme (UNEP) is responsible for coordinating responses to environmental issues within the United Nations system. It was established by Maurice Strong, its first director, after the United Nations Conference on ...
called for ozone layer research that same year, and, in 1981, authorized a global framework convention on ozone layer protection. In 1985, Joe Farman, Brian G. Gardiner, and Jon Shanklin published the first scientific paper detailing the hole in the ozone layer. That same year, the Vienna Convention was signed in response to the UN's authorization. Two years later, the
Montreal Protocol The Montreal Protocol is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances that are responsible for ozone depletion. It was agreed on 16 September 1987, and entered into force ...
, which regulated the production of CFCs was formally signed. It came into effect in 1989. The U.S. formally phased out CFCs in 1995.


Aerosol propellants

If aerosol cans were simply filled with compressed gas, it would either need to be at a dangerously high pressure and require special
pressure vessel A pressure vessel is a container designed to hold gases or liquids at a pressure substantially different from the ambient pressure. Construction methods and materials may be chosen to suit the pressure application, and will depend on the size o ...
design (like in
gas cylinder A gas cylinder is a pressure vessel for storage and containment of gases at above atmospheric pressure. High-pressure gas cylinders are also called ''bottles''. Inside the cylinder the stored contents may be in a state of compressed gas, vap ...
s), or the amount of payload in the can would be small, and rapidly deplete. Usually, the gas is the
vapor In physics, a vapor (American English) or vapour (British English and Canadian English; see spelling differences) is a substance in the gas phase at a temperature lower than its critical temperature,R. H. Petrucci, W. S. Harwood, and F. G. Her ...
of a liquid with
boiling point The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the surrounding env ...
slightly lower than
room temperature Colloquially, "room temperature" is a range of air temperatures that most people prefer for indoor settings. It feels comfortable to a person when they are wearing typical indoor clothing. Human comfort can extend beyond this range depending on ...
. This means that inside the pressurized can, the vapor can exist in equilibrium with its bulk liquid at a pressure that is higher than
atmospheric pressure Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1013.25 millibars, ...
(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 Miscibility () is the property of two substances to mix in all proportions (that is, to fully dissolve in each other at any concentration), forming a homogeneous mixture (a solution). The term is most often applied to liquids but also applies ...
with the payload or dissolved in the payload. In gas dusters and
freeze spray Freeze spray (cold spray or vapocoolant) is a type of aerosol spray product containing a liquified gas used for rapidly cooling surfaces, in medical and industrial applications. It is usually sold in hand-held spray cans. It may consist of vario ...
s, the payload itself acts as the propellant. The propellant in a gas duster can is not "compressed air" as sometimes assumed, but usually a
haloalkane The haloalkanes (also known as halogenoalkanes or alkyl halides) are alkanes containing one or more halogen substituents. They are a subset of the general class of halocarbons, although the distinction is not often made. Haloalkanes are widely u ...
.
Chlorofluorocarbon Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are fully or partly halogenated hydrocarbons that contain carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F), produced as volatile derivatives of methane, ethane, and p ...
s (CFCs) were once often used as propellants, but since the
Montreal Protocol The Montreal Protocol is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances that are responsible for ozone depletion. It was agreed on 16 September 1987, and entered into force ...
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 ozone layer or ozone shield is a region of Earth's stratosphere that absorbs most of the Sun's ultraviolet radiation. It contains a high concentration of ozone (O3) in relation to other parts of the atmosphere, although still small in rel ...
. The most common replacements of CFCs are mixtures of volatile
hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ...
s, typically
propane Propane () is a three-carbon alkane with the molecular formula . It is a gas at standard temperature and pressure, but compressible to a transportable liquid. A by-product of natural gas processing and petroleum refining, it is commonly used as ...
, n-
butane Butane () or ''n''-butane is an alkane with the formula C4H10. Butane is a gas at room temperature and atmospheric pressure. Butane is a highly flammable, colorless, easily liquefied gas that quickly vaporizes at room temperature. The name but ...
and
isobutane Isobutane, also known as ''i''-butane, 2-methylpropane or methylpropane, is a chemical compound with molecular formula HC(CH3)3. It is an isomer of butane. Isobutane is a colourless, odourless gas. It is the simplest alkane with a tertiary carbo ...
.
Dimethyl ether Dimethyl ether (DME; also known as methoxymethane) is the organic compound with the formula CH3OCH3, (sometimes ambiguously simplified to C2H6O as it is an isomer of ethanol). The simplest ether, it is a colorless gas that is a useful precursor ...
(DME) and
methyl ethyl ether Methoxyethane, also known as ethyl methyl ether, is a colorless gaseous ether In organic chemistry, ethers are a class of compounds that contain an ether group—an oxygen atom connected to two alkyl or aryl groups. They have the general f ...
are also used. All these have the disadvantage of being
flammable A combustible material is something that can burn (i.e., ''combust'') in air. A combustible material is flammable if it ignites easily at ambient temperatures. In other words, a combustible material ignites with some effort and a flammable mat ...
.
Nitrous oxide Nitrous oxide (dinitrogen oxide or dinitrogen monoxide), commonly known as laughing gas, nitrous, or nos, is a chemical compound, an oxide of nitrogen with the formula . At room temperature, it is a colourless non-flammable gas, and ha ...
and
carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...
are also used as propellants to deliver foodstuffs (for example,
whipped cream Whipped cream is liquid heavy cream that is whipped by a whisk or mixer until it is light and fluffy and holds its shape, or by the expansion of dissolved gas, forming a firm colloid. It is often sweetened, typically with white sugar, an ...
and
cooking spray Cooking spray is a spray form of an oil as a lubricant, lecithin as an emulsifier, and a propellant such as food-grade alcohol, nitrous oxide, carbon dioxide or propane. Cooking spray is applied to frying pans and other cookware to prevent fo ...
). Medicinal aerosols such as
asthma inhaler A metered-dose inhaler (MDI) is a device that delivers a specific amount of medication to the lungs, in the form of a short burst of aerosolized medicine that is usually self-administered by the patient via inhalation. It is the most commonly used ...
s use hydrofluoroalkanes (HFA): either
HFA 134a 1,1,1,2-Tetrafluoroethane (also known as norflurane (INN), R-134a, Freon 134a, Forane 134a, Genetron 134a, Green Gas, Florasol 134a, Suva 134a, or HFC-134a) is a hydrofluorocarbon (HFC) and haloalkane refrigerant with thermodynamic properties ...
(1,1,1,2,-tetrafluoroethane) or HFA 227 (1,1,1,2,3,3,3-heptafluoropropane) or combinations of the two. More recently, liquid
Hydrofluoroolefin Hydrofluoroolefins (HFOs) are unsaturated organic compounds composed of hydrogen, fluorine and carbon. These organofluorine compound are of interest as refrigerants. Unlike traditional hydrofluorocarbons (HFCs) and chlorofluorocarbons (CFCs), whic ...
(HFO) propellants have become more widely adopted in aerosol systems due to their relatively low vapor pressure, low
global warming potential Global warming potential (GWP) is the heat absorbed by any greenhouse gas in the atmosphere, as a multiple of the heat that would be absorbed by the same mass of carbon dioxide (). GWP is 1 for . For other gases it depends on the gas and the time ...
(GWP), and nonflammability. Manual pump sprays can be used as an alternative to a stored propellant. Liquid aerosol propellant filling machines require additional precautions, such as being mounted externally to the production warehouse in a gas house. Liquid aerosol propellant machines are typically constructed to comply with ATEX Zone II/2G regulations (classification Zone 1).


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 (steel with a layer of tin) and may be made of two or three pieces of metal crimped together.
Aluminium can An Aluminum can (British English: Tin can) is a single-use container for packaging made primarily of aluminum. It is commonly used for food and beverages such as milk and soup but also for products such as oil, chemicals, and other liquids. Globa ...
s are also common and are generally used for products that are more expensive or intended to have a more premium appearance, such as personal care products. The valve is crimped to the inside rim of the can, and the design of this component is important in determining the spray rate. The actuator is depressed by the user to open the valve; a spring closes the valve again when it is released. The shape and size of the nozzle in the actuator controls the aerosolized particle size and the spread of the aerosol spray.


Non-propellant packaging alternatives

True aerosol sprays release their propellant during use. Some non-propellant alternatives include various spray bottles, squeeze bottles, and Bag on Valve (BoV) or Bag in Can (BiC) compressed gas aerosol systems. Packaging that uses a piston barrier system by
CCL Industries CCL Industries Inc. is a Toronto, Ontario-based company founded in 1951. It describes itself as the world's largest label maker. It is listed on the Toronto Stock Exchange, and is an S&P/TSX 60 Component. CCL consists of five divisions – ...
or EarthSafe by
Crown Holdings Crown Holdings, Inc., formerly Crown Cork & Seal Company, is an American company that makes metal beverage and food cans, metal aerosol containers, metal closures and specialty packing. Founded in 1892, it is headquartered in Yardley, Pennsylvan ...
is often selected for highly
viscous The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the in ...
products such as post-foaming
hair gel Hair gel is a hairstyling product that is used to harden hair into a particular hairstyle. History Analysis of ancient Egyptian mummies has shown that they styled their hair using a fat-based gel. The researchers behind the analysis say tha ...
s, thick
creams Cream is a dairy product composed of the higher-fat layer skimmed from the top of milk before homogenization. In un-homogenized milk, the fat, which is less dense, eventually rises to the top. In the industrial production of cream, this process ...
and
lotion Lotion is a low-viscosity topical preparation intended for application to the skin. By contrast, creams and gels have higher viscosity, typically due to lower water content. Lotions are applied to external skin with bare hands, a brush, a clean ...
s, food spreads and industrial products and
sealant Sealant is a substance used to block the passage of fluids through openings in materials, a type of mechanical seal. In building construction ''sealant'' is sometimes synonymous with '' caulking'' and also serve the purposes of blocking dust, so ...
s. The main benefit of this system is that it eliminates gas permeation and 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 consistent flow rate with minimal product retention. Another type of dispensing system is the bag-in-can (or BOV, bag-on-valve technology) system where the product is separated 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, is suitable for all-attitude, (360-degree) dispensing, quiet and non-chilling discharge. One key performance difference relative to true aerosol systems is that traditional BoV dispensing pressures, BoVs pressurized solely by pressurized gas) drops as the product is dispensed. This bag-in-can system is used in the packaging of pharmaceutical, industrial, household, pet care and other products that require complete separation between the product and the propellant or require near complete evacuation of thin to viscous formulations. A later development is the 2K (two component) aerosol spray, with a main component stored in a main chamber, and a second component stored in an accessory container. When an applicator activates the 2K aerosol by breaking the accessory container, the two components mix. The 2K aerosol can is advantageous for delivery of reactive mixtures; for example, a 2K reactive mixture can use low
molecular weight A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bio ...
monomer In chemistry, a monomer ( ; '' mono-'', "one" + '' -mer'', "part") is a molecule that can react together with other monomer molecules to form a larger polymer chain or three-dimensional network in a process called polymerization. Classification ...
,
oligomer In chemistry and biochemistry, an oligomer () is a molecule that consists of a few repeating units which could be derived, actually or conceptually, from smaller molecules, monomers.Quote: ''Oligomer molecule: A molecule of intermediate relati ...
, and functionalized low molecular
polymer A polymer (; Greek '' poly-'', "many" + '' -mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...
to make a final
cross-linked In chemistry and biology a cross-link is a bond or a short sequence of bonds that links one polymer chain to another. These links may take the form of covalent bonds or ionic bonds and the polymers can be either synthetic polymers or natural ...
high molecular weight polymer. A 2K aerosol can increase solid contents and deliver high-performance polymer products, such as curable
paint Paint is any pigmented liquid, liquefiable, or solid mastic composition that, after application to a substrate in a thin layer, converts to a solid film. It is most commonly used to protect, color, or provide texture. Paint can be made in many ...
s,
foam Foams are materials formed by trapping pockets of gas in a liquid or solid. A bath sponge and the head on a glass of beer are examples of foams. In most foams, the volume of gas is large, with thin films of liquid or solid separating the ...
s, and
adhesive Adhesive, also known as glue, cement, mucilage, or paste, is any non-metallic substance applied to one or both surfaces of two separate items that binds them together and resists their separation. The use of adhesives offers certain advant ...
s.


Safety concerns

Aerosol cans have three main areas of health concern: * Contents may be deliberately inhaled to achieve
intoxication Intoxication — or poisoning, especially by an alcoholic or narcotic substance — may refer to: * Substance intoxication: ** Alcohol intoxication ** LSD intoxication ** Toxidrome ** Tobacco intoxication ** Cannabis intoxication ** Cocaine in ...
from the propellant (known as inhalant abuse or "huffing"). Calling them "canned air" or "cans of compressed air" could mislead the ignorant to think they are harmless; in fact, such misuse has caused deaths. *
Aerosol burn An aerosol frostbite of the skin is an injury to the body caused by the pressurized gas within an aerosol spray cooling quickly, with the sudden drop in temperature sufficient to cause frostbite to the applied area. Medical studies have noted an i ...
injuries can be caused by the spraying of aerosol directly onto the skin, in a practice sometimes called "frosting". Adiabatic expansion causes the aerosol contents to cool rapidly on exiting the can. *The propellants in aerosol cans are typically combinations of ignitable gases and have been known to cause fires and explosions. However, non-flammable compressed gases such as nitrogen and nitrous oxide have been widely adopted into a number of aerosol systems such as air fresheners and aerosolized whipped cream, as have non-flammable liquid propellants. *In later 2021 and through 2022, a large number of consumer aerosols were recalled due to the presence of
Benzene Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms ...
in their finished products. Where the recall was far reaching, Benzene is considered a trace contaminant in some but not all hydrocarbon propellants. Though rigorous testing at both the propellant manufacturer and the aerosol filling site, unsuitable aerosol propellants can be detected and destroyed prior to use in any finished products. In the United States, non-empty aerosol cans are considered
hazardous waste Hazardous waste is waste that has substantial or potential threats to public health or the environment. Hazardous waste is a type of dangerous goods. They usually have one or more of the following hazardous traits: ignitability, reactivity, cor ...
, but are still considered "recyclable when empty" in US curbside recycling programs.


See also

* Aerosol paint * Fabrican *
Graffiti Graffiti (plural; singular ''graffiti'' or ''graffito'', the latter rarely used except in archeology) is art that is written, painted or drawn on a wall or other surface, usually without permission and within public view. Graffiti ranges from s ...
* Silly String


References


External links


Consumer Aerosol Products Council


{{Authority control Norwegian inventions Products introduced in 1927 Articles containing video clips Packaging