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’ve definitely heard his ideas.

He was born in 1881 in Bennington, Vermont, USA. He apprenticed as a machinist and was promoted to third assistant engineer before joining the Traveler Insurance Company, where he became the assistant superintendent of the Engineering and Inspection Division. He retired there in 1956 and died in 1962.

What did HW Heinrich do?

Unlike many who try to bring him down, Heinrich was not an “insurance salesman”. He was a graduate engineer and taught safety at New York University for over 20 years. During World War I, he served as an Engineering Officer in the United States Navy. He was appointed chairman of the security section of the United States Army War Advisory Board during World War II and became a Fellow of the American Society of Safety Engineers in 1961.

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

Why you should care about this

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

  • there is a mathematical relationship between the number of similar accidents and their severity;
  • the most common cause of occupational accidents is unsafe behavior by employees; and
  • reducing the overall frequency of workplace accidents will lead to a similar reduction in the number of serious injuries.

These are the basic principles of many current safety programs such as Behavior Based Safety; Zero Harm (or zero whatever) and so on, which are being vigorously promoted by consultancies and adopted by companies and security professionals.

So what were these concepts?

Heinrich’s loss control triangle

Heinrich obtained workplace injury data from insurance claims and from workplaces (usually supervisors). None of this data is available today, nor was there enough information in Heinrich’s books or notes to allow it to be duplicated.

From analysis of the data, Heinrich proposed that for every major injury, there are 29 minor injuries and 300 no-injury accidents. Most health and safety practitioners would have seen some variation of this formula in presentations with triangles with differently colored horizontal bands representing different severity of injuries and the relationships between them. These are mostly used by proponents of Behavior Based Safety (BBS) programs and are often referred to as 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 proportions. However, at the fourth revision (1959), they only applied to similar incidents with similar causes involving the same person.

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Heinrich’s severity classification was also very different from what is commonly discussed today in presentations using this concept. Heinrich viewed a serious injury as one that had to be claimed with a workers’ compensation insurer or reported to a government agency, regardless 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 reviewed these classifications, as well as the actual relationships between them, and qualified the results by stating that they would be different for each workplace and time.

Heinrich’s theories of accident causation and prevention

Henry suggested that:

  • 88% of occupational accidents were caused by unsafe actions (usually by the injured person);
  • 10% of workplace accidents resulted from unsafe equipment or conditions; and
  • the remaining 2% were unavoidable.

In his domino theory, Heinrich argued that injuries resulted from accidents; accidents due to unsafe practices which in turn arose from the mistakes of individuals that originated in the social environment. Injuries are best prevented by avoiding accidents. Because the direct cause of accidents were unsafe practices, eliminating them has been the most effective focus of injury prevention programs. Does this sound familiar? As the BBS and other psychology-based safety programs support, changing employee behavior should be the number one way to reduce the number and severity of workplace injuries.


In a book of almost 500 pages many other things are discussed, but these are the concepts that people encounter most often – even though Heinrich is rarely credited as the originator of these ideas. So as it may seem, these ideas are not new, but have become commonplace within the security industry. However, given their age, they should not be accepted blindly, but re-examined in the light of modern workplaces and work practices.