Not all chemicals are bad. Without chemicals such as hydrogen and oxygen, for example, there would be no way to make water, a vital ingredient in beer.―Dave Barry
Oxygen is essential for us to stay alive, rather for the Earth to work right. Oxygen is required everywhere, and this already nominal section of the atmospheric air is decreasing more and more. Earlier, people used to breathe in twice as much as oxygen that we breathe in today. Oxygen concentrators increase the oxygen level in the atmospheric air where they are ignited. These generators, or concentrators, are used in aquariums, food sterilization, oxygen bar, oxygen therapy, laboratories, and some agricultural uses as well. They are devices that discharge oxygen as a result of a chemical reaction. The source is generally an inorganic superoxide, chlorate or perchlorate. Ozonides are also strong oxygen sources.
An oxygen concentrator is ignited with a firing pin, and the chemical reaction that takes place is usually exothermic, which makes the generator a fire hazard. These generators are very quiet, portable, and maintenance-free, since they have very few moving parts. They are so small that they can be used in combination with an existing generator system as well. In these generators, air is used as the gas that is fed, and its efficiency decreases in humid conditions. There is another system that utilizes the molecular sieves to split air into its elements, which are then directed towards the commercial system that uses up the oxygen and discharges other gases. This kind of process is absolutely opposite to the cryogenic separation of gases.
These kinds of oxygen concentrators are used in commercial airlines also, as they provide emergency oxygen to passengers from the pressure drop in the cabin. Though they are not used in the cockpit or for the cockpit crew, they are placed above each and every row in an airplane. In case of decompression, the panels are either opened automatically by the automatic pressure switch or by a manual switch. Pressing the switch releases the masks. Once the passengers pull down the masks, they remove the retaining pins that trigger oxygen production. In the core, the oxidizer has sodium chlorate that is mixed with less than 5 percent barium peroxide, and less than one percent of potassium perchlorate. Lead styphnate and tetracene are mixed, and they form the explosive in the percussion cup. The chemical reaction that occurs is exothermic, and the temperature of the canister reaches well above 260 degrees C. This process produces oxygen for about fifteen to twenty minutes. The diameter of the two-mask generator is usually 63 mm or 2.5 inches, and is 223 mm or 8.8 inches long, whereas, the diameter of the three-mask generator is 70 mm or 2.8 inches, and length is 250 mm or ten inches long.
An oxygen candle is a kind of oxygen generator that is cylindrical in shape, and contains a mixture of sodium chlorate and iron powder. The mixture smolders when ignited at about 600 degrees C, gives sodium chloride and iron oxide as a by-product, apart from 6.5 man-hours of oxygen per kilogram of the mixture. The release of oxygen takes place at a fixed rate. The mixture can be stored as long as required, even for twenty years. The process that the reaction follows would be clinically called thermal decomposition. The heat that is produced is due to the burning of iron. The candle is generally wrapped in a thermal insulation, so that the temperature can be maintained and the equipment around can also be protected from the heat generated. These generators are used in aircraft, firefighter's breathing apparatus, submarines, and the like, where a small and portable oxygen concentrator generator with a long shelf-life is required.