A chemical oxygen generator, or solid fuel oxygen generator (SFOG, or TGK in Russian) is a device that releases oxygen created by a chemical reaction. The oxygen source is usually an inorganic superoxide, chlorate or perchlorate. A promising group of oxygen sources are ozonides.

The generators are usually ignited mechanically, by a firing pin.

The chemical reaction is usually exothermic, making the generator a potential fire hazard. Accidental activation of improperly shipped expired generators caused the ValuJet Flight 592 crash.

Potassium superoxide was used as an oxygen source on early manned USSR space missions, in fire fighting, and mine rescue.

Oxygen candle

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A chlorate candle, or an oxygen candle, is a cylindrical chemical oxygen generator containing a mix of sodium chlorate and iron powder. When ignited, the mixture smolders at about 600 °C, producing sodium chloride, iron oxide, and about 6.5 man-hours of oxygen per kilogram of the mixture. It releases oxygen at a fixed rate. The mixture has an indefinite shelf life if stored properly; candles stored for 20 years have shown no decrease in oxygen output. The oxygen is released by thermal decomposition, the heat is supplied by the burning iron. The candle has to be wrapped in thermal insulation to maintain the reaction temperature and to protect surrounding equipment.

Potassium and lithium chlorate, and sodium, potassium and lithium perchlorates can also be used in oxygen candles.

Solid oxygen generator from MIR

The TGK generator contains a replaceable cartridge, a thin walled steel tube with a three-part block of oxygen releasing mixture based on lithium perchlorate. Two parts are tablets of the chemical mixture and the third one is the igniter tablet with a flash igniter. The igniter is struck by a firing pin when the device is activated. One cartridge releases 600 liters of oxygen and burns for 5-20 minutes at 450-500 °C. The oxygen is cooled and filtered from dust and odors, and released into the space station atmosphere. ^*

On 23 February 1997, during the exchange of an air filter, a failed chemical oxygen generator spewed torch-like jet of a molten metal and sparks across one of the Mir space station modules, burning for 14 minutes and blocking the escape route to one of the Soyuz spacecraft. ^* The accident was caused by a leak of the lithium perchlorate from one of the canisters.

Uses

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Chemical oxygen generators are used in aircraft, breathing apparatus for firefighters and mine rescue crews, submarines, and everywhere where a compact emergency oxygen generator with long shelf life is needed. They usually contain a device for absorption of carbon dioxide, often a filter filled with lithium hydroxide; a kilogram of LiOH absorbs about half a kilogram of CO₂.

Self-contained self-rescue devices (SCSRs) are used to facilitate escape from mines.

On the International Space Station, chemical oxygen generators are located aboard the Elektron module. Each canister can produce enough oxygen for one crewmember for one day.

Human spaceflight | Firefighting equipment | Submarines