Chemical oxygen generator
A chemical oxygen generator 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
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 in a fixed rate. The mixture has an indefinite shelf life; candles stored for 20 years shown no decrease of 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 keep the reaction temperature and to protect the surrounding equipment.
Potassium and lithium chlorate, and sodium, potassium and lithium perchlorates can be used in oxygen candles as well.
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 chemical. Two parts are tablets of the chemical mixture, 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, 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. [1]
Uses
Chemical oxygen generators are used in airplanes, breathing apparatuses 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, usually a filter filled with lithium hydroxide; a kilogram of LiOH absorbs about half kilogram of CO2.