Accident Investigation

Resources - Accident Investigation and Root Cause Analysis

Catching the Hazards that Escape Controls

In the ideal safety and health scenario, the employer knows precisely the hazards and potential hazards to which employees could be exposed and has designed a perfect system of prevention and control.  In real life, some hazards may escape detection during the inventory process.  Others have a way of slipping out of the controls set up to protect workers.  So, you need ways to catch these hazards and get them controlled, or better controlled, before anyone gets hurt.

OSHA's Safety and Health Program Management Guidelines recommend a complete worksite analysis to provide the basis for hazard prevention and control.  This analysis includes identifying all hazards and potential hazards through comprehensive surveys, change analysis, and routine hazard analysis; regular site inspections; employee reports of hazards; accident and near-miss investigations; and analysis of injury and illness trends over time.


Inspections are the best understood and most frequently used tool of worksite analysis.  Much has been written about them, and many inspection checklists are available in other publications.  For a general checklist for small businesses or a starting point for larger businesses, OSHA recommends the checklist found in OSHA Publication 2209 (Revised 1992), "OSHA Handbook for Small Businesses."

In this discussion, we will consider some aspects of inspections that are frequently not covered in other publications.

What Do We Mean By Regular Site Inspections?

The term inspection refers to looking closely at something to see if it meets requirements.  At your worksite, several kinds of inspections probably are done, some of them at fixed intervals.  In OSHA's Safety and Health Program Management Guidelines, the term "regular site inspection" means a general inspection of every part of the worksite to locate any hazards that need correction.  This includes routine industrial hygiene monitoring and sampling.

Inspection Frequency.

The regular site inspection is done at specified intervals.  OSHA recommends that medium and large fixed worksites be inspected completely at least every quarter, with some part of the inspection occurring each month.  For construction sites, OSHA recommends site inspections at least weekly because of the rapidly changing nature of the site and its hazards.

At small fixed worksites, the entire site should be inspected at one time.  And even for the smallest worksite, inspections should be done at least quarterly.  If the small worksite uses hazardous materials or involves hazardous procedures or conditions that change frequently, inspections should be done more often.  Small business employers can contact the local office of the OSHA-funded, State-run consultation service for help in determining the most appropriate frequency for inspections.

What Should Be Inspected?

A methodical inspection will follow a checklist based on the inventory of hazards and the preventive actions and controls designed to reduce or eliminate worker exposure.  Regular site inspections should be designed to check each one of those controls to make sure that hazards are contained. 

Hazards may be controlled by engineering.  Examples of engineering controls are the guards placed on equipment to prevent hand or body contact with tools or machinery that can cut or pinch body parts or catch clothing, hair, or body parts and pull them into the machinery.  These guards should be checked during inspections to make sure they are in good working order and remain in place during operations.  Another example of an engineering control of hazards is the ventilation system that carries away air contaminants.  The velocity of the ventilation system should be checked periodically.  Depending on the risk of the contaminant controlled, periodic air sampling may also be needed.

You also can control hazards with specifically designed work practices and procedures.  An example is the precautions taken by a production equipment operator when restarting after a jam.  The inspector should keep an eye out for any unauthorized modifications of these work practices.

Still another way to control hazards is through personal protective equipment (PPE).  Meat cutters, for example, should wear protective mesh gloves.  Many varied types of worksites require safety glasses or hearing protection devices in designated areas.  The inspector will want to examine the equipment to ensure its good condition.  Just as important, the inspector should see whether employees are wearing required PPE and whether the equipment is being worn appropriately.  This includes, for example, stopping workers who have placed disposable hearing protection only partway into their ears and have left most of the plug protruding.  The inspector will insist that the PPE be worn as intended.

Do not overlook areas outside of the production mainstream.  Your search for common hazards and OSHA standards violations should cover the entire worksite, including all office areas.  In addition to the checklist in the "OSHA Handbook for Small Businesses," you may find useful the inventory list at the back of this chapter.

Who Should Inspect?

Ideally, medium and large worksites will have more than one type of regular site inspections.

Supervisors. Many employers make it the supervisor's responsibility to inspect his/her work area at the beginning of every shift to ensure that equipment and personnel are ready to work safely.  This can be particularly helpful when other shifts use the same area and equipment or when after-hours maintenance and cleaning are routinely done.  Supervisors' inspections of their own areas should not substitute, however, for the broad general inspection recommended in the OSHA Guidelines.  There are two reasons for this:

  • Those who work in an area can start "not seeing" things that they get used to.  It is always good to have cross-inspections where supervisors or employees from one area look at another area.
  • A general site inspection will encompass areas not assigned to individual supervisors, for example, outdoor and other common areas.

Employees. OSHA recommends involving employees in the safety and health program, in both problem identification and resolution.  One way to do this is to have the employee committee or the joint employee-management committee conduct routine inspections.  By employing this method, you:

  • Expand the number of people doing inspections, and therefore, improve the odds of finding hazards; and
  • Increase employee awareness of the safety and health program.

Safety and Health Staff. It is most common and most logical for the staff personnel who specialize in safety and health to conduct the inspections.  Even when other employees conduct inspections, it is wise also to involve the specialists.  In a small business, the specialist may be the Human Resources Director or another member of management with many important duties in addition to safety and health.  By having the safety and health staffer conduct inspections, you:

  • Keep the person responsible for safety and health in touch with the successes and/or problems in the hazard prevention and control program and
  • Use your greatest in-house source of expertise.

What Training Should Inspectors Have?

Safety and Health Staff. Personnel responsible for developing the safety and health program should have, at a minimum, the equivalent of the OSHA Training Institute Course #501, "A Guide to Voluntary Compliance in Safety and Health." Additional training is needed for large worksites and small worksites with hazardous operations or materials.

For advice about training and specific information about the training that OSHA offers, write or call:

The OSHA Training Institute
1555 Times Drive
Des Plaines, Illinois 60018
(847) 297-4913

Cost for private-sector course participants is minimal and is based on the number of days of training.  For the Institute fiscal year beginning October 1993, tuition ranged from $82 for a 2-day course to $484 for a 10-day course, with the 5-day Course #501 costing $237.

Supervisors. All supervisors should have training in the hazards that workers under their supervision are likely to encounter, plus training in how to control these hazards.  When they are responsible for area inspections, supervisors also should have specific training in how to inspect.  Formal coursework may not be necessary, but the training should be provided by someone who is knowledgeable.

Employees. All employees should understand the potential hazards to which they might be exposed and the ways they can protect themselves and their fellow workers.  Those who are involved in inspections need training in recognizing and controlling all the potential hazards of the worksite.  They will also need written guidance, tips for inspecting, and some on-the-job training by safety and health staff or other specialists.


In all but the smallest and least dangerous of workplaces, written inspection reports are necessary to record the hazards discovered, responsibility assigned for correction and tracking of correction to completion.

Having a written record will help ensure:

  • Assignment of responsibility for hazard correction,
  • Tracking of correction to completion,
  • Identification of problems in the controls system when the same type of hazards keep appearing even after correction is verified,
  • Identification of problems in the accountability system and
  • Identification of hazards for which no prevention or control has been planned.

Of course, having such written records will be most helpful if they are read by someone knowledgeable in the safety and health program.  This person then can provide top managers with summaries of problems.


If correction cannot be accomplished immediately after the discovery of a hazard, the inspection report should include whatever interim protective measures have been taken, and should not be considered closed until the final correction has been made.  A written tracking system will improve your inspection program.  And the best tracking system is written right into your inspection report form. 

Important things to remember about regular site inspections and follow-up:

  • These inspections should cover every part of the worksite;
  • They should be done at regular intervals, with frequency depending upon the size of the worksite and the nature of the hazards;
  • In-house inspectors should be trained to recognize hazards and to bring fresh vision to work areas being examined;
  • Found hazards must be tracked to correction; and
  • Information from inspections should be used to expand the inventory of hazards and/or improve the hazard prevention and control program.


Employees play a key role in helping you discover and control the hazards that may develop -- or that already exist -- in your workplace.  They have a unique and valuable perspective on procedures and conditions.

A reliable system for employee reporting is an important element of an effective safety and health program.  Such a system is characterized by:

  • A genuine company or worksite policy that is consistent with other policies and that encourages employees to report their concerns about safety and health conditions or possible hazards in work practices,
  • Timely and appropriate responses to the reporting employee,
  • Timely and appropriate action valid concern exists,
  • Tracking of any required hazard correction and
  • Protection of reporting employees from official and unofficial harassment.


You have decided what your policy will be concerning employee reporting.  The next step is to ensure that all employees understand the policy.  Further, they need to be made aware that the policy is genuine.  In larger worksites, the policy should be typed and placed on bulletin boards, distributed to all employees, and discussed in weekly or monthly safety meetings.  In the smallest worksites, it may be sufficient to gather everyone together, go over the policy, and then invite discussion or questions.  You will know that you have done enough when every employee, when asked, can tell you what the policy is.

The written policy is a good place to affirm your intention to protect employees from harassment or reprisal of any kind. 


Having employees report hazards will not work if they cannot see reasonable results in a reasonable amount of time.  You can give your employee a preliminary response when extra time is needed to analyze a reported hazard.  Many larger workplaces assign special maintenance codes to work orders that involve safety or health.  The code requires the maintenance supervisor to give that work a higher priority.  When complete correction of a hazard requires ordering parts or materials and a wait of several months, give your employee a status update from time to time.  You will be sending a message that his/her concern has not been forgotten.

Important: when the preferred corrective measures cannot be accomplished immediately, it is your responsibility to provide interim protection to your workers.  You must take whatever steps may be feasible to temporarily eliminate or control the hazard.

Results must not only be timely, but must also alleviate the employee's concern.  If management decides that no hazard exists, the reason behind this judgment should be thoroughly explained to the reporting employee.  Care should be taken to express gratitude for the employee's erring on the side of safety and health.  It is better to have some non-hazards reported than to overlook even one real hazard because a worker believed that management would not respond.

If you are uncertain whether the reported practice or condition is hazardous, further checking needs to be done.  If a good description can be given over the phone, or photographs or drawings made that reveal the situation, you can call or visit the nearest Federal or State OSHA office for advice.  Small businesses can contact the nearest office of the OSHA-funded, State-run consultation service.

If your employee has discovered a real hazard, the action that you take to correct it should be appropriate and swift.


Each valid hazard identified through employee reports of hazards should be tracked to complete correction.  Hazards that are quickly corrected may not present a problem for long-term tracking, but a record of the correction will help in determining where management systems have broken down should the same hazard reappear.  Different management measures may be needed for hazards that do not stay corrected, as contrasted with those that do not get corrected.  For hazards that require complicated or time-consuming corrections, a system of tracking is needed to make sure that the final correction is not forgotten in the press of other matters.  Additionally, tracking long-term hazard correction enables management to keep the reporting employee better informed.


It is important that employees know that reporting a hazard will not result in any official or unofficial harassment or reprisal from management, individual supervisors, or coworkers.  The policy on employee reports of hazards should make this clear.  In addition, there are several steps you can take to help ensure that harassment is never considered:

  • Avoid performance evaluations that rate supervisors negatively for employee reports of hazards in their areas as long as they are responding appropriately to the reports.
  • Separate employee reports of hazards from the disciplinary system.  For example, avoid placing policy statements dealing with these two subjects close together on a bulletin board or in sequence in an employee handbook.  Such physical proximity can give the impression that one employee can get another in trouble by reporting him or her for hazardous practices.
  • Approach all discussions and written descriptions of employee reporting of hazards as a group effort to keep the worksite safe and healthful.  Emphasize the positive.
  • Emphasize the responsibility that each employee has for coworkers' safety and health as well as for his/her own.  The safety and health of individual employees is everyone's business.
  • If you discover a case of harassment for reporting a hazard, enforce your policy clearly and emphatically.


There are several ways that employees can report hazards.  The most common are:

  • Oral reports to supervisors,
  • Suggestion programs,
  • A hazard card program,
  • Maintenance work orders, and
  • Written forms that provide for anonymity.

Many larger worksites will use a combination of some or all of these systems.

Oral reports. At every worksite employees should be able to report hazards to their supervisors.  When the supervisor is properly trained and accepts his/her responsibility for the safety and health of the workers under supervision, informal oral reporting can occur naturally.  When an employee's concerns appear valid, the supervisor then has the responsibility to either correct the hazard, request correction by maintenance, or ask for assistance from the safety department.

Most worksites encourage this type of reporting.  Used alone, however, it does not provide for hazard correction tracking.  Nor does it enable you to look for trends and patterns.  And it provides little protection from supervisors who may not be sufficiently concerned about health and safety.

At very small worksites, where "everybody knows everything," this oral system may be all that is needed.  OSHA recommends, however, that you at least adopt a simple written system where the supervisor makes a short report of each hazard reported and the action taken. 

Suggestion Programs. The most frequently used type of written system is a program where employees are encouraged to make safety and health suggestions.  This is a very positive approach.  Not only does it provide for reporting unsafe conditions and acts, but it also encourages employees to come up with imaginative new ways of doing things safely and healthfully.  If a suggestion program is used for hazard reporting, however, management must be sure that collection points are checked several times a day and that suggestions are read at the time of collection.  This will ensure that identified hazards get corrected in a timely manner.

If the suggestion program is the sole means of reporting hazards or the only written system, management must encourage employees to use the system for all types of hazard reporting, and not just for ideas in the "It would be nicer if..." category.

A hazard card program. Many medium and large worksites develop or purchase a program for employee hazard reporting.  One such program includes a format for training employees in basic hazard recognition.  It uses cards on which employees jot down unsafe conditions and practices.  These cards usually are turned in to the safety department for checking and tracking of any valid hazard correction.

Some workplaces give awards for the highest number of cards with valid concerns turned in over a specific period of time.  Others have set quotas for the number of cards turned in.  The success of these special uses seems to depend upon the "culture" of the worksite.

Maintenance work orders. For unsafe conditions, maintenance usually will have to make the correction.  Some companies give every employee the right to fill out a maintenance work order.  Others allow employees to fill them out but require supervisory sign-off before orders are sent to the maintenance department.

This system for employee hazard reporting should be used only if there is a special high priority safety and health code for maintenance work orders.  With such a code, the maintenance supervisor is required to give hazard correction work orders higher priority than maintenance for production improvement only.  Copies of coded work orders should be carried immediately to the Safety Department (or person responsible for safety and/or health) so that correction tracking can begin.

This special code also helps your safety and health staff look for patterns that may become apparent over time and that call for closer scrutiny of conditions or practices.

The work order system for employee reporting of hazards is not sufficient if used alone.  While it can lead to correction of hazardous conditions, it cannot correct hazardous practices.  And this system is not useful for encouraging imaginative new approaches to improving conditions and procedures.

Written Forms. Some of the systems described above involve the use of forms.  The best written system for your worksite may be one that you devise especially for employee reports of hazards.  You can allow for anonymity, when desired, by not requiring the reporting employee to either sign his/her name or give the completed form to the supervisor.  You can post your response to an anonymous report on a bulletin board in the area mentioned in the report. 

For all the reporting systems discussed above, some variations will work better for your site than others.  The important points to remember are:

  • Have a policy that encourages employee reports of hazards,
  • Make this policy well known and understood,
  • Protect reporting employees from harassment,
  • Respond in an appropriate and timely manner,
  • Track all hazards to correction and
  • Use the information you obtain about hazards to revise your hazard inventory and/or to improve your hazard prevention program.


Much has been written about investigating accidents, and many elaborate charts have been devised to assist the investigator.  In this chapter, OSHA will not attempt to duplicate all the information readily available elsewhere.  (A good publication available from the National Safety Council is "Accident Investigation...A New Approach." For this and other materials, contact the NSC, P.O. Box 558, Itasca, IL 60143, telephone (800) 621-7619.)

Accident/incident investigation is another tool for uncovering hazards that either were missed earlier or have managed to slip out of the controls planned for them.  It is useful only when done with the aim of discovering every contributing factor to the accident/incident in order to "foolproof" the condition and/or activity and prevent future occurrences.  In other words, your objective is to identify root causes.


The National Safety Council defines "accident" as "an unplanned, undesired event that results in personal injury or property damage." It defines "incident" as "an unplanned, undesired event that adversely affects completion of a task." An illness that results from a single occurrence comes within the term "personal injury." This term does not include occupational illness resulting from long-term exposure to health hazards.

What Should Be Investigated?

Since all accidents result in property damage or personal injury, they should be investigated to determine the contributing causes and actions needed to prevent future occurrences.  Since incidents could result in property damage or personal injury, these, too, should be investigated.  "Near-misses" fall into this latter category.  This term describes incidents where no property was damaged and no personal injury sustained, but where, given a slight shift in time or position, damage and/or injury easily could have occurred.

Who Should Investigate?

The usual investigator for all incidents is the supervisor in charge of the involved area and/or activity.  At a minimum, the safety department or the person in charge of safety and health should review these investigations and provide for another level of investigation when:

  • The event had very serious results,
  • The nature of the event is very complex,
  • The event involved more than one supervisor’s responsibilities and/or
  • The initial investigation did not clearly establish a full range of contributing factors and/or preventive actions.

Many companies use a team or a subcommittee of the joint employee-management committee to investigate accidents involving serious injury or extensive property damage.  This may supplant the supervisor's investigation or may serve as a second-level investigation.  When a team or committee investigates, the team leader or chairperson must have enough authority and status in the organization to do whatever is needed.

Training for Incident Investigation.

No one should investigate accidents or incidents without appropriate accident investigation training.  Many safety and health consultants and professional organizations provide this type of training.  Before you commit resources to training, you might want to check the course contents against the information found in the National Safety Council's booklet, "Accident Investigation. . .A New Approach." After your investigators have received training, you should follow up by checking investigative reports to see if the training is being put to good use.

Results Desired.

The investigation report, regardless of length or style of presentation, should document all applicable facts.  The report should include thorough interviews of everyone with any knowledge of the event.  Six key questions should be answered: who, what, when, where, why, and how. Fact should be distinguished from opinion, and both should be presented carefully and clearly.  A good investigation is likely to reveal several contributing factors, and it probably will recommend several preventive actions.

You will want to avoid the trap of laying sole blame on the injured employee.  Even if injured workers openly blame themselves for making a mistake or not following prescribed procedures, the investigator must not be satisfied that all contributing causes have been identified.  The error made by the employee may not be even the most important contributing cause.  The employee who has not followed prescribed procedures may have been encouraged directly or indirectly by a supervisor to "cut corners." The prescribed procedures may not be practical, or even safe, in the eyes of the employee.  Sometimes elaborate and difficult procedures are required, when engineering redesign might be a better answer.  In such cases, management errors -- not employee error -- may be the most important contributing causes.

All supervisors and others who investigate accidents/incidents should be held accountable for describing causes carefully and clearly.  When reviewing investigation reports, the safety department or in-house safety expert should be on the lookout for catch-phrases, for example, "Employee did not plan job properly." While such a statement may suggest an underlying problem with this worker, it is not conducive to identifying all possible causes, preventions, and controls.  Certainly, it is too late to plan a job when the employee is about to do it.  Further, it is unlikely that safe work will always result when each employee is expected to plan procedures alone.

Recommended preventive actions should make it very difficult, if not impossible, for the event to recur.  The investigative report should list all the ways to "foolproof" the condition or activity.  Considerations of cost or engineering should not enter at this stage.  Top management should have the benefit of the investigator's complete thinking before making decisions about prevention.  Some recommended actions will be capable of immediate accomplishment.  Others may take time, planning, and capital expenditure.

Use of Accident Investigations.

The primary purpose of accident/incident investigations is to prevent future occurrences.  Therefore, the investigation should be a springboard to corrective action.  Ensure results by tracking the measures you choose to their completion.

Beyond this immediate use, apply the information obtained through the investigation to update and revise your inventory of hazards and/or your program for hazard prevention and control.


OSHA's Safety and Health Program Management Guidelines list the analysis of "injury and illness trends over time, so that patterns with common causes can be identified and prevented," as the last action under Worksite Analysis.  A review of OSHA illness and injury logs is the most common form of pattern analysis.  These logs are not, however, the only useful source of such information.  Any records of hazards can be analyzed for patterns.  Examples are inspection records and employee hazard reporting records.

Pattern Analysis of the OSHA Log of Injury and Illness

Period of time covered. A record being analyzed for patterns must contain enough entries to allow patterns to emerge.  A worksite with few employees or very little hazardous work may require a review of 3 to 5 years of records.  Because a site is small or does little hazardous work does not mean, however, that pattern analysis is useless.  Even if an office operation has only one or two injuries each year, a 5-year review may indicate uncontrolled cumulative trauma hazards or lack of attention to tripping hazards.  Larger sites will find useful information in yearly, quarterly, or monthly reviews.

What to look for. Similar injuries or illnesses indicate a hazard or type of hazard that has not been controlled yet.  Diagnostic clues can be traced by noting where the injuries or illnesses occurred, what type of work was being done, the time of day, any similarities of equipment, etc.  Injuries need not be identical.  They can be, for example, to the same part of the body.  Obviously, repetitions of the same type of injury or illness indicate that hazard controls are not working adequately.

Any clue that suggests a previously unnoticed connection between several injuries or illnesses is worth further investigation.

Pattern Analysis of Inspection Records and Employee Hazard Reports.

Hazard identification should be occurring more frequently than incidents/accidents.  It should be possible, therefore, to uncover patterns in hazard identification records over shorter periods of time than may be needed to analyze patterns in incidents.  Repeat hazards, just like repeat injuries, mean that controls are not working.  Upgrading a control may be as simple as improving accountability.  (Of course, what is simple is not always easy.)

The causes of hazards can be investigated using techniques similar to those developed to find the causes of accidents. 


Even after you have conducted comprehensive hazard surveys, analyzed each workplace change for hazards, routinely analyzed jobs and/or processes for hazards, and developed a program of hazard prevention and control, there still will be some hazards in your worksite.  These hazards may have been missed, or measures taken may not have been adequate to maintain prevention or control over time.

This chapter has examined additional techniques for learning more about these persistent hazards, their correction, and effective and continuing control.  Regular site inspections; employee reports of hazards; accident/incident investigations; and analyses of patterns of illness and injury, incidents, and hazards will help complete your safety and health program.

Source: Missouri Department of Labor and Industrial Relations

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Copyright ©2000-2019 Geigle Safety Group, Inc. All rights reserved. Federal copyright prohibits unauthorized reproduction by any means without permission. Disclaimer: This material is for training purposes only to inform the reader of occupational safety and health best practices and general compliance requirement and is not a substitute for provisions of the OSH Act of 1970 or any governmental regulatory agency. CertiSafety is a division of Geigle Safety Group, Inc., and is not connected or affiliated with the U.S. Department of Labor (DOL), or the Occupational Safety and Health Administration (OSHA).