June 27, 2001
What is an accident and why should
it be investigated?
By Maureen Alvarez, CIH, CSP
term "accident" can be defined as an unplanned event
that interrupts the completion of an activity, and that may
(or may not) include injury or property damage. There are
many reasons to conduct a workplace accident investigation,
- to fulfill the legal requirement
- to determine the cost of an accident
- to determine compliance with applicable safety
- to process workers' compensation claims
importantly accident investigations are conducted to find
out the cause(s) of accidents and to prevent similar accidents
in the future. When accidents are investigated, the emphasis
should be concentrated on finding the root cause(s) of the
accident rather than the investigation procedure itself.
should do the accident investigating?
an investigation should be conducted by an expert in accident
causation who is experienced in investigative techniques,
fully knowledgeable of the work processes, procedures, persons,
and industrial relations environment of a particular situation.
Unfortunately, such persons are hard to find. Especially in
smaller organizations, both workers and supervisors with little,
if any,previous investigative experience maybe called upon
to participate in an accident investigation.
and how many people should investigate an accident?
best team to conduct an accident investigation includes the
injured worker, their supervisor and a safety representative. It
is critical that the injured worker’s supervisor is on the
accident investigation team because this person will be the
most knowledgeable about the work conditions and the people
involved. Furthermore, the supervisor can usually take immediate
remedial action if an immediate corrective action is identified.
Other members that are valuable to the accident investigation
team include maintenance, engineering, process support and
other technical staff members that have a good understanding
of the incident and the corrective action.
to make sure that investigators are impartial?
who believes that accidents are caused by unsafe conditions
will likely try to uncover conditions as causes. On the other
hand, one who believes they are caused by unsafe acts will
attempt to find the human errors that are causes. Therefore,
it is necessary to examine briefly some underlying factors
in a chain of events that ends in an accident.
important point is that even in the most seemingly straightforward
accidents, seldom, if ever, is there only a single cause. For
example, an "investigation" which concludes that
an accident was due to worker carelessness, and goes no further,
fails to seek answers to several important questions such
- Was the worker distracted? If yes, why was
the worker distracted?
- Was a safe work procedure being followed?
If not, why not?
- Were safety devices in order? If not, why
- Was the worker trained? If not, why not?
that answers these and related questions will probably reveal
conditions that are more open to correction than attempts
to prevent "carelessness."
are the steps involved in investigating an accident?
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
- Investigate the accident
- Identify the causes
- Report the findings
- Develop a plan for corrective action
- Implement the plan
- Evaluate the effectiveness of the corrective
changes for continuous improvement
time as possible should be lost between the moment of an accident
or near miss and the beginning of the investigation. This
approach allows the investigator to observe the conditions
as they were at the time, prevent disturbance of evidence,
and identify witnesses. It is recommended that you have a
pre-assembled “toolbox” prepared when you need to conduct
an accident investigation. The tools that members of the
investigating team may need are pencil, paper, camera, film,
tape measure, statement forms, etc. These items should be
immediately available so that time is not wasted.
What should be looked at as the cause of an accident?
models of accident causation have been proposed, ranging from
Heinrich's domino theory to the sophisticated Management Oversight
and Risk Tree (MORT). A simple model 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
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
- Were the appropriate tools and materials
- Were they used?
- Were safety devices working properly?
- Was lockout used when necessary?
most of these questions, an important follow-up question is
"If not, why not?"
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
- Should personal protective equipment (PPE)
have been used?
- Was the PPE used?
each time the answer reveals an unsafe condition, the investigator
must ask why this situation was allowed to
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
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? (how many hours had they
- Were they under stress (work or personal)?
holds the legal responsibility for the safety of the workplace
and therefore the role of supervisors and higher management
must always be considered in an accident investigation. Answers
to any of the preceding types of questions logically lead
to further questions such as:
safety rules communicated to and understood by all employees?
- Were written procedures 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
- Were unsafe conditions corrected?
- Was regular maintenance of equipment carried out?
- Were regular safety inspections carried out?
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.
How are the facts collected?
may want to take photographs before anything is moved, both
of the general area and specific items. Careful study of these
may reveal conditions or observations missed previously. Sketches
of the accident scene based on measurements taken may also
help in subsequent analysis and will clarify any written reports.
Broken equipment, debris, and samples of materials involved
may be removed for further analysis by appropriate experts.
Even if photographs are taken, written notes about the location
of these items at the accident scene should be prepared.
useful background source, but often overlooked, is the information
that can be found in documents such as technical data sheets,
maintenance reports, past accident reports, formalized safe-work
procedures, and training reports. Any pertinent information
should be studied to see what might have happened, and what
changes might be recommended to prevent recurrence of similar
Why should recommendations be made?
The most important final step is to come up
with a set of well-considered recommendations designed to
prevent recurrences of similar accidents. Once you are knowledgeable
about the work processes involved and the overall situation
in your organization, it should not be too difficult to come
up with realistic recommendations. Resist the temptation
to make only general recommendations to save time and effort.
In the unlikely event that you have not been
able to determine the causes of an accident with any certainty,
you probably still have uncovered safety weaknesses in the
operation. It is appropriate that recommendations be made
to correct these deficiencies.
Remember, the purpose of an accident investigation
is to determine the cause(s) of the incident and to implement
corrective actions in order to prevent this accident from
happening again. A thorough accident investigation is always
worth the time and effort!
For additional information regarding accident
investigations and accident prevention, please refer to the
many links located on our safety page located on the Osh.Net
home page at http://www.osh.net/directory/safety/index.htm
Copyright © 2001 by WorkCare™ All
See you next month,