Home > Emergency Response, Safety, Security > What Happens When Something Happens? Part 2

What Happens When Something Happens? Part 2

Accident Causation

As little time as possible should be lost between the moment of an accident or near miss and the beginning of the investigation. In this way, one is most likely to be able to observe the conditions as they were at the time, prevent disturbance of evidence, and identify witnesses. The tools that members of the investigating team may need (pencil, paper, camera, film, camera flash, tape measure, etc.) should be immediately available so that no time is wasted.

The accident investigation process involves the following steps:

  • Report the accident occurrence to a designated person within the organization
  • Provide first aid and medical care to injured person(s) and prevent further injuries or damage
  • Investigate the accident
  • Identify the causes
  • Report the findings
  • Develop a plan for corrective action
  • Implement the plan
  • Evaluate the effectiveness of the corrective action
  • Make changes for continuous improvement

Accident Causation Models

Many models of accident causation have been proposed, ranging from Heinrich’s domino theory to the sophisticated Management Oversight and Risk Tree (MORT).

The simple model shown here attempts to illustrate that the causes of any accident can be grouped into five categories – task, material, environment, personnel, and management. When this model is used, possible causes in each category should be investigated. Each category is examined more closely below. Remember that these are sample questions only: no attempt has been made to develop a comprehensive checklist.


Here the actual work procedure being used at the time of the accident is explored. Members of the accident investigation team will look for answers to questions such as:

  • Was a safe work procedure used?
  • Had conditions changed to make the normal procedure unsafe?
  • Were the appropriate tools and materials available?
  • Were they used?
  • Were safety devices working properly?
  • Was lockout used when necessary?

For most of these questions, an important follow-up question is “If not, why not?”


To seek out possible causes resulting from the equipment and materials used, investigators might ask:

  • Was there an equipment failure?
  • What caused it to fail?
  • Was the machinery poorly designed?
  • Were hazardous substances involved?
  • Were they clearly identified?
  • Was a less hazardous alternative substance possible and available?
  • Was the raw material substandard in some way?
  • Should personal protective equipment (PPE) have been used?
  • Was the PPE used?
  • Were users of PPE properly trained?

Again, each time the answer reveals an unsafe condition, the investigator must ask whythis situation was allowed to exist.


The physical environment, and especially sudden changes to that environment, are factors that need to be identified. The situation at the time of the accident is what is important, not what the “usual” conditions were. For example, accident investigators may want to know:

  • What were the weather conditions?
  • Was poor housekeeping a problem?
  • Was it too hot or too cold?
  • Was noise a problem?
  • Was there adequate light?
  • Were toxic or hazardous gases, dusts, or fumes present?


The physical and mental condition of those individuals directly involved in the event must be explored. The purpose for investigating the accident is not to establish blame against someone but the inquiry will not be complete unless personal characteristics are considered. Some factors will remain essentially constant while others may vary from day to day:

  • Were workers experienced in the work being done?
  • Had they been adequately trained?
  • Can they physically do the work?
  • What was the status of their health?
  • Were they tired?
  • Were they under stress (work or personal)?


Management holds the legal responsibility for the safety of the workplace and therefore the role of supervisors and higher management and the role or presence of management systems must always be considered in an accident investigation. Failures of management systems are often found to be direct or indirect factors in accidents. Ask questions such as:

  • Were safety rules communicated to and understood by all employees?
  • Were written procedures and orientation available?
  • Were they being enforced?
  • Was there adequate supervision?
  • Were workers trained to do the work?
  • Had hazards been previously identified?
  • Had procedures been developed to overcome them?
  • Were unsafe conditions corrected?
  • Was regular maintenance of equipment carried out?
  • Were regular safety inspections carried out?

This model of accident investigations provides a guide for uncovering all possible causes and reduces the likelihood of looking at facts in isolation. Some investigators may prefer to place some of the sample questions in different categories; however, the categories are not important, as long as each pertinent question is asked. Obviously there is considerable overlap between categories; this reflects the situation in real life.

Again it should be emphasized that the above sample questions do not make up a complete checklist, but are examples only.

[Proceed to third of four parts]

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  1. July 18, 2012 at 10:41 PM

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