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Toner refilling is the practice of refilling empty laser printer toner cartridges with new toner powder. This enables the cartridge to be reused, saving the cost of a complete new cartridge and the impact of the waste and disposal of the old one.

While toner cartridges are commonly refilled with results reported to be good, in at least some cases refilling without full remanufacturing may leave waste toner from each print and paper debris in the cartridge, potentially causing backgrounding problems and producing contamination in the refilled cartridge.^[1]

The U.S. patent for the "Refillable toner cartridge" was issued to Fred Keen on March 28, 1989. ^[2]

There are several different methods for refilling cartridges:

Toner cartridges cannot be refilled indefinitely, because mechanical parts such as rollers wear out. Some cartridges include the electro-optical drum, which becomes depleted and can be scratched. Organizations refilling cartridges for resale usually clean and test each cartridge to ensure that it is fit for reuse and resale. While several sources offer empty inkjet cartridges to be refilled^{[citation needed]}, brand new empty OEM laser cartridges are not easily found. Also, some models of laser print engines, like most inkjet printers, communicate with "chips" or fuses inside the toner cartridge which indicate that the cartridge is exhausted, whether or not it actually is. Some research is usually required to determine the feasibility of refilling a particular cartridge.

In general, DIY refilling requires opening a cartridge designed not to be opened, refilling it with toner, and capping the opening that was made to gain access. Some cartridges can be disassembled; others require a hole to be drilled or melted.

Toners vary in composition; manufacturers make toner designed for their own printers, and a generic toner may not work as well. In some cases there may be separate additions of toner and "developer". Refilling kits include printer-specific instructions.

The following basic types of refill toner (differing mainly in particle size and fusing temperature) have been identified by one vendor while other refill vendors insist that each printer or copier model requires a unique type.^{[citation needed]}

1. HP, Canon printers
2. Canon PC copiers
3. IBM/Lexmark Optra and similar
4. Epson EPL, NEC Silentwriter
5. Xerox and Sharp
6. Samsung and Lexmark Optra E
7. Brother

Kits are available to refill the 4 toner cartridges used by colour printers (cyan, magenta, yellow and black), or to fill a single cartridge. Kits include a reset chip where necessary. In all cases a toner that is at least compatible must be used.

While there are environmental benefits to refilling the toner cartridges of laser printers, a refilled cartridge may produce inferior print quality and reliability.^[3]

1. Refilling cartridges either by the end user, or as a service, is claimed by most printer manufacturers and toner remanufacturers to be harmful to both the quality and reliability of the prints, the cartridge as well as the life of the printers.^[4]
2. Life cycle assessments may indicate that recycling is a preferable option.^[3]
3. The quality of third party toners can vary immensely, and it is also important that the toner is appropriate for the particular printer.

Common problems can include:

1. Insufficient lubricant in the toner, leading to drum, developer unit or cleaning blade damage.
2. Wrong melting point, leading to fouling in the fusing unit, print rubbing off, etc.
3. Wrong electrostatic properties or particle size, leading to a dirty machine and poor quality print.
4. Large amounts of loose toner in the machine can also cause fouling and damage to the mechanisms, and air filters can become clogged, causing overheating.^{[citation needed]}

Companies and individuals that refill toner, however, indicate that in most cases the cost benefits of refilling outweigh the possible disadvantages.^[5]

This section needs expansion. You can help by adding to it. (April 2008)

As a fine powder, toner can remain suspended in the air for some period, and is considered to have health effects comparable to inert dust. It can be an irritant to people with respiratory conditions such as asthma or bronchitis.

Toner powder is not toxic but does need to be handled with care, as carbon black (one of its components) has been classified as a nuisance dust, designated by the International Agency for Research on Cancer as a possible carcinogen.^[6] Carbon black may contain impurities known to be carcinogens which may lead to small growths, irritated eyes, headache, itching skin and direct contact with toner can lead to skin and eye sensitisation.^[7] Health and safety regulations must be considered when handling, transporting and storing toner powders.

Safety precautions include the use of gloves, and a protective dust mask to prevent inhalation. If spilled toner is cleaned with a standard vacuum cleaner the toner may become electrically charged and catch fire, and is so fine that it passes through filters and can escape into the room or the vacuum cleaner motor.

• "The environmental impact of reuse vs. recycling of toner and inkjet cartridges" (PDF). Brussels: EuroVAprint ASBL. 2014.