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Oxygen Systems - Chemical Oxygen Generators

In lieu of an oxygen bottle, a chemical oxygen generator can be used as an oxygen source. Chemical oxygen generators normally use sodium chromate (NaClO3) along with smaller amounts of other chemicals and convert this chemical to oxygen flow when the source is activated. The release of oxygen from the sodium chromate is accomplished by igniting the chemical. When converting the sodium chromate to oxygen a byproduct of the chemical reaction is heat and hence the generator can get very warm (500 degF is possible). In addition, there is a tendency for debris/dirt/grime/etc that has collected on the generator over time in service to burn causing an unpleasant odor (which is usually not a safety hazard).

An example of a chemical oxygen generator is shown in Figure 1. This figure shows a passenger oxygen mask box assembly that contains 3 passenger masks that are connected to a fairly small chemical oxygen generator. This example is from a commercial aircraft. Combining the chemical oxygen generator with the passenger masks allows for a self-contained unit that does not need a separate oxygen source, such as a bottle. In this case, oxygen will flow to the masks for as long as the chemical in the generator lasts. The duration of the oxygen availability from a chemical oxygen generator is determined by the amount of sodium chromate contained with the generator.



Figure 1 Chemical Oxygen Generator


Special precautions are required when using chemical oxygen generators due to the high temperature of the bottle during oxygen conversion and the presence of oxygen in the vicinity of the heat source. This can lead to a fire or burning if some item around the chemical oxygen bottle would be ignitable at 500 degF. Consequently, separation and shielding of the other equipment from the chemical oxygen bottle must provide a sufficient insulator. The box or structure surrounding the oxygen bottle as well as any valves, hoses, etc. in the box must be able to withstand the heat. The US Department of Transportation labels chemical oxygen bottles as hazardous equipment when transporting. When handling or transporting chemical oxygen bottles, proper safety precautions in line with the US DOT regulations should be followed.