Canned air
Encyclopedia
Aerosol spray
Aerosol spray is a type of dispensing system which creates an aerosol mist of liquid particles. This is used with a can or bottle 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 or mist...
, which have a straw that draws from the bottom of the can). Despite the name "canned air," the cans actually contain gases that are much easier to compress into liquids, such as difluoroethane, trifluoroethane
1,1,1-Trifluoroethane
1,1,1-Trifluoroethane, or R-143a or simply trifluoroethane, is a fluorocarbon compound that is a clear, colorless gas. It should not be confused with the isomeric compound 1,1,2-trifluoroethane.It has a critical temperature of 73 °C....
, or tetrafluoroethane (the main components of air, which are oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
and nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
, are in fact very rarely used). Hydrocarbon
Hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....
s, like butane
Butane
Butane is a gas with the formula C4H10 that is an alkane with four carbon atoms. The term may refer to any of two structural isomers, or to a mixture of them: in the IUPAC nomenclature, however, butane refers only to the unbranched n-butane isomer; the other one being called "methylpropane" or...
, were often used in the past, but their flammability forced manufacturers to use fluorocarbon
Fluorocarbon
Fluorocarbons, sometimes referred to as perfluorocarbons or PFCs, are organofluorine compounds that contain only carbon and fluorine bonded together in strong carbon–fluorine bonds. Fluoroalkanes that contain only single bonds are more chemically and thermally stable than alkanes...
s.
Cleaning
A gas duster is usually used to clean or dust delicate items or reach difficult areas. The dusters are particularly useful on ventilation fans and electronic heat sinkHeat sink
A heat sink is a term for a component or assembly that transfers heat generated within a solid material to a fluid medium, such as air or a liquid. Examples of heat sinks are the heat exchangers used in refrigeration and air conditioning systems and the radiator in a car...
s, which collect dust readily, and are otherwise very difficult to clean. The gases themselves do not leave residues on sensitive equipment, however the bitterant
Bitterant
A bitterant is a chemical that is added to a product to make it smell or taste bitter. Bitterants are commonly used as aversive agents to discourage the inhalation or ingestion of toxic substances.-Examples of use:...
added to prevent abuse will leave a residue, making gas dusters an inappropriate choice for cleaning anything users will come into contact with such as keyboards. They can create static unless a specific ESD
Electrostatic discharge
Electrostatic discharge is a serious issue in solid state electronics, such as integrated circuits. Integrated circuits are made from semiconductor materials such as silicon and insulating materials such as silicon dioxide...
-safe compound is added.
The can must be held upright during use. Inverting, tilting or even shaking the can during use will result in the unevaporated liquid being forced through the nozzle instead of gas. The liquid will boil away almost instantly outside the can, producing extreme cold in the process. This sudden drastic change in temperature can mar or damage surfaces (as well as cause frostbite if it contacts skin).
Cooling
When the can is held upright and activated, gas flows out through the nozzle. The pressure inside the can therefore drops, and is no longer sufficient to keep the contents as a liquid; so some of the liquid boils, until the equilibrium pressure is re-established. The vaporizationVaporization
Vaporization of an element or compound is a phase transition from the liquid or solid phase to gas phase. There are three types of vaporization: evaporation, boiling and sublimation....
of a liquid is endothermic
Endothermic
In thermodynamics, the word endothermic describes a process or reaction in which the system absorbs energy from the surroundings in the form of heat. Its etymology stems from the prefix endo- and the Greek word thermasi,...
; thus, heat is absorbed, and the can becomes cold.
Continued use over a short period of time results in the can becoming increasingly cold. As the temperature drops, the vapor pressure
Vapor pressure
Vapor pressure or equilibrium vapor pressure is the pressure of a vapor in thermodynamic equilibrium with its condensed phases in a closed system. All liquids have a tendency to evaporate, and some solids can sublimate into a gaseous form...
of the liquid also drops, resulting in decreasing force of the gas at the nozzle. At some point, the force of the ejected gas at the nozzle is insufficient to accomplish anything useful in terms of dust removal. When the temperature of the can reaches the boiling point
Boiling point
The boiling point of an element or a substance is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid....
of the liquid (which is -25C for difluoroethane), the liquid no longer evaporates into gas in any useful quantity. At this point, one must stop and wait for the can to return to room temperature before it will again provide sufficient gas flow. Alternating between two cans (allowing one to warm while the other is being used) is one way to work around this problem during an extensive dusting job. Warming the can with a heat source can be dangerous as the can may overheat and explode.
A related category of product has an internal dip tube that reaches just about to the bottom of the can, so it sprays the liquid. It evaporates very quickly, seriously chilling anything it touches the way dry ice (solid CO2) would. These "chill spray" cans were used by trained, responsible adults who troubleshot electronic equipment by chilling suspected components to make the equipment fail, if extreme cold would be a cause.
Alternative to 134a
Many gas dusters contain HFC-134a1,1,1,2-Tetrafluoroethane
1,1,1,2-Tetrafluoroethane, R-134a, Genetron 134a, Suva 134a or HFC-134a, is a haloalkane refrigerant with thermodynamic properties similar to R-12 , but with less ozone depletion potential...
(tetrafluoroethane), which is widely used as a propellant and refrigerant. HFC-134a sold for those purposes is often sold at a much higher unit 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, though in most cases, 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
Airsoft
Airsoft is a sport in which participants shoot round non-metallic pellets launched via replica firearms.Gameplay varies in style and composition but often range from short-term skirmishes, organized scenarios, military simulations, historical reenactments, to competition target shooting events...
gas guns, which use HFC-134a as a source of 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.
Safety
Since gas dusters are one of the many inhalantInhalant
Inhalants are a broad range of drugs whose volatile vapors are taken in via the nose and trachea. They are taken by volatilization, and do not include drugs that are inhaled after burning or heating...
s that can be easily abused, many manufacturers have added a bittering
Bitterant
A bitterant is a chemical that is added to a product to make it smell or taste bitter. Bitterants are commonly used as aversive agents to discourage the inhalation or ingestion of toxic substances.-Examples of use:...
agent to deter people from inhaling the product. Because of the generic name "canned air", some people mistakenly believe that the can only contains normal air or contains a less harmful substance such as nitrous oxide
Nitrous oxide
Nitrous oxide, commonly known as laughing gas or sweet air, is a chemical compound with the formula . It is an oxide of nitrogen. At room temperature, it is a colorless non-flammable gas, with a slightly sweet odor and taste. It is used in surgery and dentistry for its anesthetic and analgesic...
. However, the gas
Gas
Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...
es actually used are denser than air, and inhaling
Inhalant
Inhalants are a broad range of drugs whose volatile vapors are taken in via the nose and trachea. They are taken by volatilization, and do not include drugs that are inhaled after burning or heating...
can lead to paralysis
Paralysis
Paralysis is loss of muscle function for one or more muscles. Paralysis can be accompanied by a loss of feeling in the affected area if there is sensory damage as well as motor. A study conducted by the Christopher & Dana Reeve Foundation, suggests that about 1 in 50 people have been diagnosed...
, serious injury, or death. Recently, in the United States and Canada stores have begun to ask for ID to verify that the customer is 18 years or older (some include Fred Meyer
Fred Meyer
Fred Meyer, Inc., is a chain of hypermarkets founded in 1922 in Portland, Oregon, by Fred G. Meyer. The company was one of the pioneers of one-stop shopping, eventually combining a complete grocery supermarket with a drugstore, clothing store, shoe store, fine jewelers, home decor store, home...
, Office Max, Office Depot
Office Depot
Office Depot is a supplier of office products and provides many services. The company's selection of brand name office supplies includes business machines, computers, computer software and office furniture, while its business services encompass copying, printing, document reproduction, shipping,...
, Best Buy
Best Buy
Best Buy Co., Inc. is an American specialty retailer of consumer electronics in the United States, accounting for 19% of the market. It also operates in Mexico, Canada & China. The company's subsidiaries include Geek Squad, CinemaNow, Magnolia Audio Video, Pacific Sales, and, in Canada operates...
, Staples
Staples
-Places:*Staples, Minnesota, United States*Staples, Texas, United States*Staples Center, an arena in Los Angeles, California*Staples High School, a high school in Connecticut*Staples , a train station in Staples, Minnesota served by Amtrak...
, RadioShack
RadioShack
RadioShack Corporation is an American franchise of electronics retail stores in the United States, as well as parts of Europe, South America and Africa. As of 2008, RadioShack reported net sales and operating revenues of $4.81 billion. The headquarters of RadioShack is located in Downtown...
, Walgreens
Walgreens
Walgreen Co. , doing business as Walgreens , is the largest drugstore chain in the United States of America. As of August 31st, the company operates 8,210 locations across all 50 states, the District of Columbia and Puerto Rico. Founded in Chicago, Illinois in 1901, and has since expanded...
, Canadian Tire
Canadian Tire
Canadian Tire Corporation, Limited is one of Canada's 60 largest publicly traded companies. The firm operates an inter-related network of businesses engaged in retailing hardgoods, apparel and petroleum as well as financial and automotive services, employing more than 58,000 people across Canada...
, Shopko, Target
Target Corporation
Target Corporation, doing business as Target, is an American retailing company headquartered in Minneapolis, Minnesota. It is the second-largest discount retailer in the United States, behind Walmart. The company is ranked at number 33 on the Fortune 500 and is a component of the Standard & Poor's...
, Maplin Electronics
Maplin Electronics
Maplin Electronics is a retailer of electronic goods in the UK and Ireland. As of December 2010, there are 180 Maplin Electronics stores in the United Kingdom...
, CVS, and Wal-Mart
Wal-Mart
Wal-Mart Stores, Inc. , branded as Walmart since 2008 and Wal-Mart before then, is an American public multinational corporation that runs chains of large discount department stores and warehouse stores. The company is the world's 18th largest public corporation, according to the Forbes Global 2000...
).
Though not extremely flammable in gaseous form, many dusters use a fluorocarbon which can burn under some conditions, and warn of this on the packaging. When inverted to spray liquid, the boiling fluorocarbon aerosol is easily ignitable, producing a very large blast of flame and extremely toxic byproducts such as hydrogen fluoride
Hydrogen fluoride
Hydrogen fluoride is a chemical compound with the formula HF. This colorless gas is the principal industrial source of fluorine, often in the aqueous form as hydrofluoric acid, and thus is the precursor to many important compounds including pharmaceuticals and polymers . HF is widely used in the...
and carbonyl fluoride
Carbonyl fluoride
Carbonyl fluoride is the chemical compound with the formula COF2. This gas, like its analog phosgene, is highly toxic. The molecule is planar with C2v symmetry.-Safety:...
as a combustion product.
Fluorocarbon
Fluorocarbon
Fluorocarbons, sometimes referred to as perfluorocarbons or PFCs, are organofluorine compounds that contain only carbon and fluorine bonded together in strong carbon–fluorine bonds. Fluoroalkanes that contain only single bonds are more chemically and thermally stable than alkanes...
s, although they replaced the older set of more flammable hydrocarbon
Hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....
s, can still combust relatively easily, e.g., by holding a source of fire (such as a match or lighter) to the escaping fluid
Fluid
In physics, a fluid is a substance that continually deforms under an applied shear stress. Fluids are a subset of the phases of matter and include liquids, gases, plasmas and, to some extent, plastic solids....
. They do, however, have a lower chance of exploding in a closed container by means of spontaneous combustion
Spontaneous combustion
Spontaneous combustion is the self-ignition of a mass, for example, a pile of oily rags. Allegedly, humans can also ignite and burn without an obvious cause; this phenomenon is known as spontaneous human combustion....
(which is what caused the general switch away from hydrocarbons).
The liquid, when released from the can, boils at a very low temperature, rapidly cooling any surface it touches. This can cause frostbite
Frostbite
Frostbite is the medical condition where localized damage is caused to skin and other tissues due to extreme cold. Frostbite is most likely to happen in body parts farthest from the heart and those with large exposed areas...
on contact with skin. As the can gets very cold during extended use, holding the can itself can result in frostbite.
Since gas dusters are often contained in pressure vessel
Pressure vessel
A pressure vessel is a closed container designed to hold gases or liquids at a pressure substantially different from the ambient pressure.The pressure differential is dangerous and many fatal accidents have occurred in the history of their development and operation. Consequently, their design,...
s, they are fairly explosively volatile.
Use of dusters can produce large clouds of dust, which may directly affect the lungs.
Environmental impacts
Difluoroethane (HFC-152a), trifluoroethane (HFC-143a), and completely non-flammable tetrafluoroethane (HFC-134a) are potent greenhouse gases. According to the Intergovernmental Panel on Climate ChangeIntergovernmental Panel on Climate Change
The Intergovernmental Panel on Climate Change is a scientific intergovernmental body which provides comprehensive assessments of current scientific, technical and socio-economic information worldwide about the risk of climate change caused by human activity, its potential environmental and...
(IPCC), the global warming potential
Global warming potential
Global-warming potential is a relative measure of how much heat a greenhouse gas traps in the atmosphere. It compares the amount of heat trapped by a certain mass of the gas in question to the amount of heat trapped by a similar mass of carbon dioxide. A GWP is calculated over a specific time...
(GWP) of HFC-152a, HFC-143a, and HFC-134a are 124, 4470, and 1430, respectively. GWP refers to global warming effect in comparison to CO2 for unit mass. 1 kg of HFC-152a is equivalent to 124 kg of CO2
Gas dusters sold in many countries are ozone
Ozone
Ozone , or trioxygen, is a triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic allotrope...
safe as they use zero-ODP gases; however, this is a separate issue from the global warming concern.
Alternatives
An air compressorGas compressor
A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume.Compressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe. As gases are compressible, the compressor also reduces the volume of a gas...
fitted with a small nozzle (as part of a compressor accessory kit) can be used in lieu for cleaning. This offers a fixed equipment cost, at the expense of portability. Care must be taken however, as water vapor may condense in the tank or at the nozzle.
Portable compressed air canisters that can be refilled with a bicycle pump
Bicycle pump
A bicycle pump is a type of positive-displacement pump specifically designed for inflating bicycle tires. It has a connection or adapter for use with one or both of the two most common types of valves used on bicycles, Schrader or Presta...
are also an option.
Electric dust blowers offer another alternative.