Air Duster.

Spray cans of air duster are useful when a printer has dust in a deep recess. Use of spray duster is appropriate where small quantities of dust are causing a problem, mechanical brushing is difficult and both water and isopropyl water would be a nuisance.

A big defect with air duster is that it just makes the dust or toner airborne. Used indoors it will settle out in the environment and some will be breathed in. Some people might think this should not be a problem for small quantities, there is a certain amount of dust in the environment anyway. Any significant quantity of dust means it might be better to take the printer outside. There is another problem: many of the chemicals used are health and /or environmental nuisance.

Ingredients.

The material is usually not compressed air because the main components of air (nitrogen and oxygen) don't compress easily and the can and its valves would need to be robust. Air dusters use the same group of propellants used for many spray products like soaps, deodorants and paints.

Air duster is typically a refrigerant so the material ships as a liquid and turns to gas in the can. Butane is sometimes used but it is highly flammable and accumulates explosively. CFCs such as Freon-12 were used until the early 1990s but the chlorine component depleted atmospheric ozone so they were banned.

The fluorocarbons used today are not ozone depleting. However some are potent greenhouse gases and chemically very stable so they will last stay in the atmosphere for a long time.

• trifluoroethane: 1,1,1-trifluoroethane aka Freon 143a and HFC-143a. It is a colourless gas with a boiling point of -47°C. It is highly flammable
• tetrafluoroethane: 1,1,1,2-Tetrafluoroethane aka HFC-134a, norflurane and histofreeze 2000 is also a colourless gas with a boiling point of -26°C. In a gas duster it will normally be taken from the top of the can, It is also used as freezer spray and taken from the bottom of the can. It is relatively inert, however its greenhouse gas contribution has resulted in some legislative restriction, for instance it is banned as a refrigerant in cars in the EU.
• Difluoroethane: 1,1-Difluoroethane is also a colourless gas with a boiling point of -25°C. Its also known as Freon 152, 152A. It is highly flammable and a potential for explosive air-vapour mixture. It doesn't deplete ozone and has a lower global warming potential. It has been used as a refrigerant but that use is largely discontinued.
• Butane: aka n-butane, methylethylethane, diethyl, liquefied petroleum gas, LPG is a colourless gas with a boiling point of 0.5°C. As its use as a fuel suggests it is highly flammable and readily forms an explosive mixture with air. It has a particularly low flash-point. Inhaled it rapidly causes suffocation and is a narcotic.

Definitive information on chemicals is best gleaned from Material Safety Data Sheets. A comprehensive collection for chemicals is found at msds.chem.ox.ac.uk. so the search phrase "butane inurl:msds.chem.ox.ac.uk" gets a web page listing Butane's properties.

Manufacturers often add a "bitterant" to make breathing canned air unpleasant. Buyers of canned air products including butane have been known to use them for "sniffing" or "huffing", deliberately breathing them in. As well as the addictive high this can cause respiratory depression, hypoxia and cardiac arrest. One of the main causes of death is that abusers inhale their own vomit. That is if they don't set fire to themselves or freeze the back of their throat. There are a great number of ways you can injure yourself by solvent abuse.

In canned air sold for electrical purposes there may also be an agent to reduce the probability of electrostatic discharge (ESD)

It may occur to you that air-duster products are either destroying the planet or threatening to destroy you. If the stuff doesn't explode it's probably raising the sea-level. If you want a narcotic please try nitrous oxide which is at least relatively harmless and has a history to it (Humphrey Davey was an early addict).

Air Compressors

Air duster raises a couple of issues suggesting it is rather undesirable: its impact on global warming and its potential for abuse. Nevertheless a quick blast of it sometimes fixes a fault and getting expensive machinery back in use must sometimes be worth it.

With some precaution you can use an air compressor instead, if you have access to one. compressed air lines are common in factories because they are used to drive production line tools, inflate tyres and even to keep generators spinning when they are not in use.

The main precaution with compressed air is that there shouldn't be any oil or water coming out of the air line (garage compressors tend to do this). Also keep the pressure quite low and don't use the compressor to spin fans - using them as turbine generators causes overvoltages. There is a possible issue with static in the air flow from compressors as well.

Experience suggests that blowing equipment out with a compressor rarely causes a problem but in principle it could blow toner dust around a workshop, blast water into an inaccessible corner or give a static jolt to a component. It's a judgement call; clean the worst of something with a brush, get stubborn residues using isopropyl, if there's still contamination blast it clean with an air line - possible outdoors or in a fume cupboard.

Cans of air-duster are possibly better for the circuitry and more convenient.