Causation model

To prevent incidents, their causes must be known.  As Louis Pasteur put it, over 100 years ago: “All things are hidden, obscure and debatable if the cause of the phenomena be unknown, but everything is clear if the cause be known.”

The model has two labels. The bottom is labelled The Problem-Solving Model, while the top is labelled The Incident Causation Model. This illustrates that the model can be used either as a problem-solving tool or a tool to explain why incidents are occurring at a site.

The problem-solving side of the model moves from the Loss section to the Inadequate Risk Assessment section.  This is what is expected from a good problem-solving model – moving from problem identification to problem causation to solution.  

The top label, namely Incident Causation Model, explains why incidents occur and provides insights about actions needed to prevent them.  

To explain the Incident Causation Model in a way that is easiest to understand it is necessary to work from the Loss, back to the Inadequate Risk Assessment.  

There are multiple causes leading to every incident.  These multiple causes work together to cause the incident.  Once the causation sequence is set in motion, it is often fortuitous or a matter of chance as to what the eventual consequences will be. 

Incidents that result in losses are called accidents.  As presented in the accident definition, these losses take the form of harm to:

Since injuries and illnesses have traditionally received so much attention, a wealth of information has been gained regarding their costs compared to the costs of property damage, down-time, and environmental spills and emissions.  Some insight to these costs was gained in the British Research previously discussed.  

While the direct costs of injuries and illnesses are significant, they represent only a small proportion of the actual costs of a company’s incidents.  In fact, since these actual costs of injuries and illnesses are often insured, many do not appreciate the impact they have on the site.  The table below contains cost items which could be used to calculate the total cost of the site’s incidents.

In addition to these fairly objective costs, there are the subjective costs of incidents which cannot be easily quantified. They include things such as:

• Public relations.
• Employee relations and morale.
• Corporate image.
• Pain, anguish, suffering.
• Psychological impact on managers and co-workers.
• Potential loss of business and markets.
• Future bargaining positions.

The costs of incidents can be illustrated as an iceberg, illustrated in Figure 4. The relatively small costs associated with insurance and medical expenses are obvious, like the tip of the iceberg, while the enormous overall costs of incidents are to be found under the surface.

It will be noticed by reviewing the iceberg that for every unit of costs, there are 6 to 53 times that amount of loss due to property, process, material and miscellaneous costs.

The iceberg has been so widely used and accepted as an illustration of the total cost of loss, that rarely are rationales given for the 6 to 53 ratio. These numbers have been derived by researching insurance cost data which supports that the costs of losses reported in the transportation industry (e.g. trucking and railroad), and various manufacturing industries alone is many times the national costs of work related injuries and illnesses.

In addition there have been numerous case studies, involving single sites or companies, which have since been done, which support these numbers as well.

For capital-intensive operations the costs tend to be on the high side; whereas for labour-intensive operations they tend to be relatively low. These costs must be carefully sought out or they will go unnoticed.

The Incident block immediately precedes the Loss.  This is where the contact with a source of energy or substance takes place.  The term Incident is used in this block because, at this point, the contact with energy or substance may or may not be above the threshold limit of the body, structure or environmental media affected.  If it does not exceed this threshold, the incident sequence stops, no loss occurs, and the event is a near-miss.  If the threshold is exceeded, harm takes place and an accident-type incident occurs.

Contacts can be classified into the following types:

• Caught between or under
• Caught in
• Caught on
• Contact with
• Contact by
• Drowning
• Different level fall (fall from elevation to lower level)
• Fall on same level
• Handling
• Exposure
• Overexertion strain
• Struck against
• Struck by
• Other

These factors imply some kind of unexpected and usually abrupt contact.  There is a principle that defines each type of contact and distinguishes one from another.

A caught between incident is one in which a person has been pinched, crushed or otherwise caught between either a moving object and a stationary object or between two moving objects.

Examples include:

• Being crushed between the rear of a truck in reverse and a loading dock.
• Having a hand pinched between a hoist chain and the load when slack is taken up.
• Having a finger caught between a door and a door jam – these are examples of being caught between a moving object and a stationary object.
• Being crushed between mill rolls.
• Having a finger pinched between two moving gears.
• Having a hand caught between a moving pulley belt and the pulley wheel – these are examples of being caught between two moving objects.

The defining principle is that two objects came together, through the movement of one or both and a person is pinched, crushed or otherwise caught between the two objects.

A caught in incident is one in which a person is trapped in some type of enclosure or a part of a person’s body is caught fast in some type of opening.

• An example of the former is a man who is trapped inside a tank as a result of the exit being blocked.  

• An example of the latter is a man stuck in a narrow opening through which he attempted to crawl.  

Caught in incidents are rare occurrences.  The defining principle is that a person (or some part of his body) has become caught in something and he cannot get out, at least not immediately.

A caught on incident is one in which a person (or some part of his clothing) has become caught on some protruding object.

• A trouser cuff caught on a projecting piece of scrap;
• An identification wristlet caught on a protruding screw;
• A glove caught on a moving machine part.

The caught on occurrences seldom result in injuries directly.  Instead, they usually trigger off other occurrences, which may or may not result in injuries.  For example, the trouser cuff caught on a piece of scrap may cause, in turn, a trip and fall accident.  The defining principle is that something protruded, that is, stuck out in such a way that a person became caught on it.

A contact with incident is one in which a person has contacted some substance or object capable of producing injury on the basis of mere non-forceful contact.

The following are examples of contact with incidents:

• Touching a hot steam pipe.
• Brushing against an energised electrical conductor.
• Stepping into scalding water.
• Contacting a corrosive chemical like sulphuric acid.

The defining principle is that the person did the contacting and that it was not the force of the contact that did the damage but the injurious characteristics of the agent contacted.

A contacted by incident is one in which a person has been contacted by some substance that has an injury-upon-contact characteristic.

Examples include:

• Being sprayed with acid.
• Spattered with molten metal.
• Contacted by live steam.
• Splashed with hot oil.
• Burned by hot gases.

The defining principle is that the person was contacted and that it was not the force of the contact that did the damage but the injurious characteristics of the contacting agent, e.g. toxic, extremely hot, extremely cold, corrosive, radio-active, electrified or otherwise injurious.

Drowning is death due to asphyxia caused by immersion in fluid, usually water. Near drowning is initial survival of a drowning accident which can lead to serious secondary complications including death; cases of near drowning therefore require attention by medical professionals. Secondary drowning is death due to chemical and biological changes in the lungs after a near drowning incident or exposure to chemicals.

A fall from elevation to lower level incident is one in which a person falls below the level on which he was standing or walking, e.g. he falls below foot level.

Examples include:

• Falling down stairs.
• Falling from a ladder.
• Falling into an open shaft.
• Falling off a scaffold.

The defining principle is that the person ended up on a level different from that on which he was standing or walking before the fall.

The same level fall incident is one in which a person falls to the same level on which he was standing or walking, e.g. he falls to foot level.

This type of incident almost invariably involves either slipping or tripping as the initial unexpected occurrence.  For that reason, such incidents are sometimes referred to as slip and fall or trip and fall accidents.

A handling incident is one in which a person suffers injury as a result of handling items which required to be lifted, pushed or pulled.

An exposure incident is one in which a person suffers injury or illness as a result of exposure to harmful conditions.

Examples include:

• Toxic gases, fumes or vapours.
• Toxic airborne particles.
• Extremes of heat or cold.
• Oxygen deficient atmospheres.
• Radioactive radiation.
• Intense light brightness’s.

It is a common practice to sub-classify such accidents according to the type of agent that caused the injury or illness.

An overstress incident is one in which a person injures himself as a result of putting excessive strain on some part of his body.

A common example is:

• A back injury sustained from awkwardly lifting a heavy object. e. overexertion injuries are usually sprains, strains, hernias, dislocations and similar type internal injuries.

The defining principle is the element of injury caused by excessive straining. 

A struck against incident is one in which a person contacts abruptly and with force some object in his surroundings.

Examples include:

• Running into another employee.
• Banging a head against a low beam.
• Striking a leg against an open drawer.
• Smashing a hand against equipment – all these are examples of struck against incidents.

The defining principle is that the person was in motion and it was he who forcefully contacted the object, not vice versa.

A struck by incident is one in which a person has been contacted abruptly and forcefully by some object in motion.

The following are examples of struck by incidents:

• Being hit by a falling tool.
• Being struck by a moving vehicle.
• Being banged into by a running employee.
• Being bumped by a rolling drum.

The person struck may be standing still or he may also be moving.  The defining principle is that some object, e.g. tool, machine, material, equipment, etc., was in or got into movement and contacted the person with force.