AHerbert Heinrich, a pioneer in workplace safety philosophy,originally suggested that workplace accidents followed a sequence of five contributing causes, and he used the image of a set of dominos to illustrate the cause and effect chain reaction that was central to his theory. Heinrich maintained that eliminating one contributing cause, like taking away one domino from the row, would prevent the chain from collapsing.

BHis original theory was published in 1931 and has since been updated and modified. In the original theory, which was later extended, the end result, or final domino in the series, was injury or damage. He stated that the immediate cause of this was an accident in the workplace. As would be expected from the 1930s worldview, Heinrich was inclined to place the blame for accidents fairly and squarely on the shoulders of the workers. A workplace accident, in his theory, was immediately attributable to unsafe acts. Although he did acknowledge that these unsafe acts might take place in a hazardous situation, he stated that these situations were generally created by, and the responsibility of, the workers. He labelled this factor as `fault of person'. Heinrich suggested that `fault of person' had its roots in the workers' ancestry or genetic factors, combined with the social environment they lived or worked in.

CThis theory was very popular, and was later updated by several other researchers in the field. The updated theory became known as the International Loss Control Institute or ILCI model. This model included two new concepts; the initial cause of workplace accidents became lack of control. This idea took some of the blame for workplace accidents away from the workers and attributed it to fundamental mistakes made at executive or management level. In keeping with a more holistic view of workplace accidents, loss of production was added as the final out come of the chain of events. Domino theories tend to be one-dimensional, however, and nowadays, we tend to believe that accidents have manifold causes.

DThe multiple causation theory assumes that there are numerous influential elements In the workplace, and that it is various permutations of these that cause accidents. The causative factors are classified as being either behavioural or environmental. Once again, behavioural influences related to the employee, and examples of such influences included an unsuitable mindset, lack of relevant knowledge or skills and/or a poor physical or mental state.

EPerhaps the simplest theory is that of pure chance, that is, that everyone is equally likely to have an accident and that there is apparently no particular identifiable cause for these; subsequently, there is no possibility of intervention. This theory seems to imply that accidents are inevitable, and that we have to accept this fact in the workplace. There are other theories with little credibility, mainly because of contradictory or inconclusive findings. The accident proneness theory is one of these. In essence, this theory states that there are always a few of us who are more susceptible to suffering mishaps, whether at work or at home, perhaps because of inattention or clumsiness.

FThere is, however, a lot of credence given to the human factors theory, which, like the domino theory, ascribes accidents to a chain of events that will lead to human error. There are three main considerations that result in human error: overload; inappropriate responses; and inappropriate activities.

GOverload can arise from the worker's competence, or rather lack thereof, which depends'on his proficiency, training, physical or mental condition, fatigue, and so on. Environmental factors also play a part in overload, for instance, excessive noise, heat or cold, insufficient lighting and distractions in the surroundings. There are internal factors which may contribute to overload as well, such as stress or anxiety from family or non work-related issues. Finally, there are situational factors, which include the level of risk inherent in the workplace, or such factors as imprecise instructions.

HInappropriate responses take into account that workers may overlook possible dangers or safety procedures, or be mismatched to the workstation. Physical factors, such as the size of the worker in relation to the load he is lifting, the force required to lift that load, and how far the worker is required to reach, are all contributing factors. Trying to carry out a workplace assignment without the necessary training, or miscalculating the degree of risk, constitutes an inappropriate activity.

IDan Petersen added to the inappropriate activity idea from the human factors theory by noting that pressure of deadlines, or the ingestion of drugs or alcohol, could contribute to worker overload, and that a `superman syndrome 'of `It won' t happen to me' should be considered as another inappropriate activity. Some workers believe themselves to be invincible or indestructible, and this results in carelessness and an unwillingness to follow safety precautions.

JObviously accident causation in industrial settings is a very complex issue and, although a number of theories have been put forward, there is not as yet one that is deemed comprehensive enough to be universally acknowledged as the `correct' one.