A typical branched chain reaction showing explosion limits

6 A typical branched chain reaction showing explosion limits 

The reaction between hydrogen and oxygen is a branched chain reaction which shows explosive regions. It has been very extensively studied, and appears to have a very complex mechanism. 

All mixtures explode above 600 °C, but in the range 450-600 °C there are certain pressures and temperatures at which reaction is explosive, while at others reaction occurs at a slow rate. These are related to the relative importance of gas phase and surface termination just balancing branching. 

A simplified mechanism illustrating the essential features of the H2/02 reaction 

H + surface — inert species O + surface — inert species OH + surface — inert species 

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