A chemical chain is a series of chemical reactions where the products of the reaction contribute to the reactants of another reaction.
These chain reactions are generally triggered by a single initial reaction where an unstable product from the first reaction becomes the reactant. This process occurs until the system reaches some stable state.
There are three "phases" to a chemical chain reaction:
Termination is the last stage where the system reaches the stable state.
The most common example of Chemical Chain is the Fire or Burning Candle.
When a flammable material is surrounded by enough oxygen and is exposed to a source of heat or temperature above the flash point, a fire starts. If there is sufficient oxygen, fuel, and heat while the fire is burning it will continue to burn until there is no longer enough of one of these three components to maintain the chemical chain reaction of the fire.