Domino Theory

The domino theory is the brain child of W.H. Heinrich who is the Assistant Superintendent of the Engineering and Inspection Division of Travelers Insurance Company. Based on his observation on the retrospective data - 75,000 injury and illness cases, in which 12,000 from insurance records and 63,000 from plant managers, actuarial and engineering reports, he devised the Heinrich Law, which is one of the well known empirical finding in his book: Industrial Accident Prevention: A Scientific Approach in 1931.

According to Heinrich, 88% of all accidents are caused by unsafe acts of people, 10% by unsafe conditions and 2% are unavoidable causes, which can be attributed as “acts of God”. Heinrich has suggested the 10 Axioms of Industrial Safety, which he considered to be the “must know” for industrial players. The 10 axioms are as below:

1. Injuries result from a series of preceding factors.
2. Accidents occur as the result of physical hazard or an unsafe act.
3. Most accidents are the result of unsafe behaviour.
4. Unsafe acts and hazards do not always result in immediate accidents and injuries.
5. Understanding why people commit unsafe acts helps to establish guidelines for corrective actions.
6. The severity of the injury is largely fortuitous and the accident that caused it is preventable.
7. Best accident prevention techniques are analogous to best quality / productivity techniques.
8. Management should assume safety responsibilities.
9. The supervisor is the key person in the prevention of industrial accidents.
10. Cost of accidents include both direct costs and indirect costs.

He proposed a “five-factor accident sequence” in which each factor would trigger the next step just like how dominoes pieces that were line-up falls upon disruption. The sequence of accident factors is as follows:

1.  Ancestry and Social Environment

A person could learn or obtain characteristics that can causes unsafe act and unsafe condition by inheritance or social environment.

2.   Worker’s Fault

The characteristics or behaviour obtained or inherited by the worker may cause him/her to making wrong decision or action that leads to unsafe act and unsafe condition.

3.    Unsafe Act and Unsafe Condition

The unsafe act and unsafe condition caused by the worker’s fault causes the accident at the workplace

4.    Accident

The accident caused by unsafe act and unsafe condition will lead to damage to the machinery and properties involved. It will also lead to injury or fatality of persons involved.

5.    Damage or Injury 

 The company will need to response to the damange and injury caused by accident.

All dominoes was down one after another.

  By eliminating the unsafe act and unsafe condition, the accident can be prevented.

Heinrich suggested that if one of the factors was being removed, it would prevent the accident, just as in removal of one of the single domino in the row would stop the action of toppling the next domino in the line, thus stop the whole chain reaction that causes damage or injury. The development of domino theory has caused the industries to blame the workers’ act as the main cause of accident. The first 3 factors in the sequence is considered as human error, and that has make the business management tends to push away their responsibility in safety to the workers, even though he has emphasized the role of management in his work.

According to Heinrich, the key domino to be removed is unsafe act & unsafe condition, which is the middle factor in the sequence. To remove the unsafe act & unsafe condition, Heinrich proposed the three “E” s corrective action sequence as below:

1. Engineering – Hazard was controlled by product design or process change.
2. Education – Staff is trained on safety procedures.
3. Enforcement – Ensure the rules and SOP on safety are followed by workers and management.