The Domino Theory states that accidents result from a chain of sequential events,
metaphorically like a line of dominoes falling over. The first person to come up with this theory was Herbert W. Heinrich- an American industrial safety pioneer from the 1930’s. The domino theory is explained in his book Industrial Accident Prevention, A Scientific Approach.
Heinrich argued that when one of the dominoes falls, it triggers the next one and the next
continuously. He further claimed that removing a key factor (such as unsafe condition or unsafe act), prevents the start of the chain reaction.
The five metaphorical dominoes labeled with accidents according to Heinrich are Social
environment and ancestry, Fault of person, unsafe act or unsafe condition, Accident, and Injury. Social environment and ancestry is the first domino in which Heinrich explains that undesirable personality traits, like greed and recklessness develop from a person’s social environment. For example a greedy person may decide to handle many tasks at the same time which leads to faults.
The traits contribute to faults of person. Fault of person is the second domino which deals with the worker personality. Heinrich explains that inborn or obtained character flaws such as bad temper and ignorance contribute at one remove to accident causation. He further claims that environmental flaws in the worker’s family or life cause secondary personal defects which are the contributors of unsafe acts, or the existence of unsafe conditions.
Unsafe act or unsafe condition is the third domino which Heinrich terms as the direct
cause of incidents. For example a worker may opt to commit an unsafe act just because there is no supervision or may be because he or she does not think the preventive measure is necessary.
The combination of the first three dominoes creates a systematic chain of events which lead to an accident. Accident is the fourth domino and In Heinrich, he says “the occurrence of a
preventable injury is the culmination of a series of events which invariably occur in a fixed and logical order. He further states that accidents are “events like falls of persons, striking of persons by flying objects that cause injury.”
Injury is the last domino which is the end result of the chain of events. Heinrich
elaborates in his “Explanation of Factors” are cuts and broken bones. He proceeds to emphasize that “the responsibility lies first of all with the employer.” His implies that a safety-conscious manager will make sure his workers strictly follow instructions, work under supervision, have remedial training and are disciplined. These remedies will assist in avoiding injuries when working.