Heinrich s Law

The origin of the Domino Theory is credited to Herbert W. Heinrich, circa 1931, who worked for Travelers Insurance. Mr. Heinrich nndertook an analysis of 75,000 accident reports by companies insnred with Travelers. This resulted in the research report titled The Origins of Accidents, which concluded that 88 percent of all accidents are caused by the unsafe acts of persons, 10 percent by unsafe physical conditions, and 2 percent are Acts of God. His analysis of 50,000 accidents showed that, in the average case, an accident resulting in the occurrence of a lost-time work injury was preceded by 329 similar accidents caused by the same unsafe act or mechanical exposure, 300 of which produced no injury and 29 resulted in minor injuries. This is sometimes referred to as Heinrich s Law. Mr. Heinrich then defined the five factors in the accident sequence, which he identified as the Domino Theory. Heinrich s work is the basis for the theory of behavior-based safety, which holds that as many as 95 percent of all workplace incidents are caused by unsafe acts. See also Accident Chain Behavior-Based Safety. 

I could not end this brief list of unfounded claims wifhouf adding the most popular myth in the field of industrial safety. This ratio between at-risk behavior and injury was first proposed in the 1930s by H. W. Heinrich (1931). It has been repeated so often, some safety pros refer to it as "Heinrich s Law." It started as a mere estimate, and after years of use in srfety speeches and publications, without any empirical verification, its status was elevated to "basic principle" or "natural law."... 

Heinrich s well-known Law of Safety implicates at-risk behavior as a root cause of most near hits and injuries (Heinrich et al., 1980). Over the past 20 years, various behavior-based research studies have verified this aspect of Heinrich s Law by systematically evaluating the impact of interventions designed to lower employees at-risk behaviors. Feedback from behavioral observations was a common ingredient in most of the successful intervention processes, whether the feedback was delivered verbally, graphically by tables and charts, or through corrective action. See, for example, the comprehensive review by Petersen, 1989, or individual research articles by Chhokar and Wallin, 1984 Geller et al., 1980 Komaki et al., 1980 and Sulzer-Azaroff and De Santamaria, 1980. 

The behavior-based approach to reducing injuries is depicted in Figure 7.1. At-risk behaviors are presumed to be a major cause of a series of progressively more serious incidents, from a near hit to a fatality. According to Heinrich s Law, there are numerous risky acts for every near hit, and many more near hits than lost-time injmies. This is fortunate news, but let us not forget that timing or luck is usually the only difference between a near hit and a serious injury. 

The Heinrich Triangle. Most safety professionals are familiar with "Heinrich s Law." As illustrated in Figure 18.4, Heinrich proposed over 60 years ago a 300 29 1 ratio between "near-miss" incidents, minor injuries, and major injuries (Heinrich, 1931 Heinrich et al., 1980). Ever since, safety professionals have been encouraged to investigate near hits in order to reduce minor and major injuries. Heinrich also estimated that 88 percent of all near hits and workplace injuries resulted from imsafe acts. As a result, some presentations of "Heinrich s Law" add a wider base to the triangle with the label "unsafe acts."... 

Heinrich Lenz studied the direction of the current that is induced in a conductor as a result of changing the magnetic field near it. You can think of this as the change in a system in electromagnetic equilibrium. Lenz published his law in 1834. It states that when a conductor interacts with a magnetic field, there must be an induced current that opposes the interaction, because of the law of conservation of energy. Lenz s law is used to explain the direction of the induced current in generators, transformers, inductors, and many other systems. 

The second relationship is Lambert s law, (named after the German physicist Johann Heinrich Lambert) which states that the intensity of a beam of parallel, monochromatic light decreases exponentially as the light travels through a thickness of homogeneous medium , expressed mathematically as... 

Babo s law /bah-bohz/ The principle that if a substance is dissolved in a liquid (solvent) the vapor pressure of the liquid is reduced the amount of lowering is proportional to the amount of solute dissolved. See also Raoult s law. The law is named for the German chemist Lambert Heinrich Clemens von Babo (1818-99). 

Hess was a Russian chemist and physician whose calorimetric measurements led him to formulate the law of constant heat summation, now known as Hess s law. His given name had several versions Germain Henri in French, as shown above Hermann Heinrich in German and German Iwanowitsch in Russian. 

Figure 10-9 The external field, Ho, causes movement of the bonding electrons around a hydrogen nucleus. This current, in turn, generates a local magnetic field opposing Hq. [You may recognize this as Lenz s law, named for Russian physicist Heinrich Friedrich Emil Lenz (1804-1865). Note that the direction of electron movement is opposite that of the corresponding electric current, which is defined as flowing from anode (-I-) to cathode (-)].

More properly called the Hagen-Poiseuille law, it was developed independently by Gotthilf Heinrich Ludwig Hagen (1797-1884) and Jean Louis Marie Poiseuille. Poiseuille s law was experimentally derived in 1838 and formulated and published in 1840 and 1846 by Jean Louis Marie Poiseuille (1797-1869). Hagen also carried out experiments in 1839. While there are a number of derivations, we follow a simple one here from Physical Chemistry by Castellan [5]. 

Heinrich law reflects a general rule between the frequency and the severity of accident, and also illustrates the randomness of accident severity or the severity lying on chance factors. Therefore, it s very difficult to control accident severity. In order to prevent major accidents, we should go all out to prevent accident occurrence, especially, attach great importance to near misses and other small accident records and reports (Wu Xu 2002). Because of small accident causing little loss, it is often easily overlooked, but it is actually a favorable indicator of the safety performance (Yu Wang 2004), which can provide comprehensive and timely feedback for safety management. 

At the age of 32, he joined the Travelers Insurance Company at Hartford, Connecticut where (except for the period of active duty during World War I) he served until his retirement in 1956 at age 74. In 1925, he was promoted to assistant superintendent of the Engineering and Inspection Division. Heinrich conducted safety courses for students at New York University for more than 20 years, beginning in 1938. In 1942, he was appointed chairman of the War Advisory Board, Safety Section, providing assistance to the U.S. Army safety effort. In 1956, he was appointed chairman and president of the Uniform Boiler and Pressure Vessels Laws Society, an organization promoting the uniformity of laws governing the safety of steam boilers and pressure vessels in the United States and Canada. Heinrich died in 1962. 

---