In a chemical chain reaction, the initial reaction creates an unstable intermediate production that leads to a subsequent reaction. The process will repeat itself until it becomes stable and reactions can't continue. Several conditions can influence the reaction, including temperature and quantity. An example of a chemical chain reaction is a fire; once ignited, the reaction must release enough heat to ignite other combustible materials.
In economic chain reactions, the idea is that growth in one sector leads to growth in another sector, or vice versa. The theory is also tied to supply and demand and the idea that through interaction, a continual chain reaction occurs where demand increases are caused by supply increases and vice versa.
In nuclear chain reactions, neutrons that were released during a fission reaction are used to produce additional fission reactions. This process continues to repeat itself through successive reactions. The reaction can be controlled, such as with nuclear power plant technology. However, uncontrolled reactions can also be disastrous, such as with nuclear weapons.
Mechanical chain reactions are influenced primarily by force and not necessarily a change like chemical or nuclear reactions. One of the most basic examples of a mechanical chain reaction is dominoes falling down one after another. The reaction starts with the first domino being pushed into the second and continues like a chain reaction until all dominoes have fallen.