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Who Was HW Heinrich, What Did He Do and Why Should You Care?

Who Was HW Heinrich, What Did He Do and Why Should You Care?

Who Was HW Heinrich?

You may or may not have heard of Herbert William Heinrich but if you’re involved in workplace safety you will have certainly heard his ideas.

He was born in 1881 in Bennington, Vermont, USA. He served an apprenticeship as a machinist and was promoted to third assistant engineer before joining the Traveller Insurance Company where he became the Assistant Superintendent of the Engineering and Inspection Division. He retired from there in 1956 and died in 1962.

What did HW Heinrich Do?

Contrary to many who attempt to put him down, Heinrich was not an “insurance salesman”. He was a qualified engineer who lectured in safety at the New York University for more than 20 years. He served as an Engineering Officer in the US Navy during the First World War. He was appointed as chair of the safety section of the US Army’s War Advisory Board during the Second World War and became a Fellow of the American Society of Safety Engineers in 1961.

The thing for which he will be remembered though is his book Industrial Accident Prevention: A Scientific Approach. The first edition was published in 1931 and he published 3 revisions in 1941, 1950 and 1959.

Why You Should Care About This

If you work in the safety field in any capacity you should care about this because the concepts of injury causation and prevention so prevalent today were first proposed by Heinrich. The most persistent of Heinrich’s concepts were:

  • a mathematical relationship exists between the numbers of accidents of similar types and their severity;
  • the most common cause of workplace accidents is unsafe acts of employees; and
  • reducing the overall frequency of workplace injuries will produce an equivalent reduction in the number of severe injuries.

These are the basic foundations of many current safety programs such as Behaviour Based Safety; Zero Harm (or zero anything) and so forth which are vigorously promoted by consultancies and adopted by firms and safety professionals.

So what were these concepts?

Heinrich’s Loss Control Triangle

Heinrich obtained data about workplace injuries from insurance claims as well as from workplaces (usually Supervisors). None of this data remains available today nor was there sufficient information in Heinrich’s books or notes to be able to duplicate it.

From analysis of the data, Heinrich proposed that for every major injury there are 29 minor injuries and 300 no-injury accidents. Most people working in health and safety would have seen some variation of this formula in presentations containing triangles with different coloured horizontal bands representing the different severity of injuries and the ratios between them. Most commonly, these are used by proponents of Behaviour Based Safety (BBS) programs and are often called Heinrich’s Triangle or Bird’s Triangle (after Frank Bird who revised Heinrich’s classifications in 1969).

Originally, Heinrich did not qualify his discussion of these ratios. However, by the fourth revision (1959) they applied only to similar incidents with similar causes involving the same individual.

Heinrich’s severity classification was also very different from what is commonly discussed in presentations today using this concept. Heinrich considered a major injury as one that required a claim to be lodged with a workers compensation insurer or reported to a state regulator irrespective of the actual severity of the injury. A minor injury was what would be considered a first aid injury in modern parlance and no injury would be a near miss. Bird revised these classifications as well as the actual ratios between them and qualified the results by indicating that they would be different for each workplace and time.

Heinrich’s Theories of Accident Causation and Prevention

Heinrich proposed that:

  • 88{efef6784ebf3f16d5e4b0b8d3ed1c43ea5828a01c7fa6aee062fb7bb1dbee174} of workplace accidents were caused by unsafe acts (usually by the injured person);
  • 10{efef6784ebf3f16d5e4b0b8d3ed1c43ea5828a01c7fa6aee062fb7bb1dbee174} of workplace accidents were the result of unsafe equipment or conditions; and
  • the remaining 2{efef6784ebf3f16d5e4b0b8d3ed1c43ea5828a01c7fa6aee062fb7bb1dbee174} were unavoidable.

In his domino theory, Heinrich argued that injuries resulted from accidents; accidents from unsafe acts which in turn occurred from the faults of individuals which had their origin in the social environment. Injuries could be best prevented by stopping accidents from happening. As the immediate cause of accidents was unsafe acts then eliminating them was the most effective focus of injury prevention programs. Does this sound familiar? It should as it underpins BBS and other psychology based safety programs – that changing the behaviour of workers is the principal means of reducing the number and severity of workplace accidents.


In a book of almost 500 pages there are many other matters discussed but these are the concepts people come across most often – even if Heinrich is seldom credited as the originator of these ideas. So, despite how it may appear these ideas are not new but have become truisms within the safety industry. However, given their age, they should not be blindly accepted but re-examined in light of modern work places and work practices.