OSHA Incident Investigation: A Guide

worker resting on site

OSHA incident investigation procedures may be more complicated than one might think. Investigating a workplace incident entails looking beyond the immediately available or perceptible information. This means that if someone gets hurt at work because they slipped on a puddle, for example, the incident report should reflect far more than the immediate facts of the incident.

Thorough incident investigations involve approaches that allow employers and employees to address any shortcomings and gaps in safety measures. By aiming to find the root causes of an incident, employers and employees will be able to prevent future incidents and make the workplace safer for all involved.

Case Study

For this article, we’ll work with a case study involving a workplace incident.

We have a manufacturing facility with machines that need to be periodically cleaned. Per the employer’s established procedures, the machines are not shut down during cleaning, exposing employees to moving machine parts.

According to the employer, the OSHA standard 29 CFR 1910.147, or the control of hazardous energy (lockout/tagout), does not apply. The employer reasons that the cleaning takes place during normal operations.

An employee begins cleaning the machines without turning them off and performing lockout tagout, which is consistent with the employer’s prescribed practices. While cleaning, a large moving part on one of the machines strikes the employee’s shoulder and causes an injury.

Part 1: Incident Investigation Basics

What are worksite incidents?

According to the Occupational Safety and Health Administration (OSHA), a worksite incident is “a fatality, injury, illness, or close call.” Incidents are events in which someone gets hurt on the job.

You’ll notice that the term also encompasses close calls, or events in which someone was close to getting hurt, but did not. This means that all incidents have to be investigated, regardless of the severity of the injury, and regardless of whether or not an injury occurred. If someone could have gotten injured in a certain situation, it counts as an incident.

Who conducts incident investigations?

Typically, supervisors conduct workplace incident investigations. However, investigations must involve managers and employees as well. Employees, in particular, have to report incidents and participate in investigations as needed.

Supervisors and managers, meanwhile, have to facilitate the following things:

  • Securing the area in which the incident occurred

  • Ensuring that the injured person receives proper medical care

  • Beginning the investigation soon after the incident

  • Notifying the right personnel, institutions, agencies, and the like

  • Identifying physical evidence, witnesses, and other possible sources of information about the incident

  • Gathering information

  • Ensuring that the investigation correctly identifies the root cause of the incident

  • Meeting regulatory and company requirements regarding worksite incidents

  • Analyzing past incidents and identifying possible trends

  • Identifying hazards and how to prevent them

While employees have a vital role to play in incident investigations, supervisors and management are ultimately the ones who are responsible for conducting investigations.

who conducts incident investigations

Management and employees have to work together during incident investigations.


What is the purpose of an incident investigation?

It’s important to remember that the purpose of an incident investigation is not to find and assign blame. Taking this approach can lend an antagonistic tone to the investigation, which will likely make employees less likely to cooperate and thus affect the investigation’s outcome.

Incident investigations aim to achieve the following:

  • Identifying the root causes of the incident

  • Identifying corrective measures to prevent future incidents

  • Improving morale among employees

  • Increasing productivity

  • Demonstrating that the employer values workplace safety

The tone of an investigation must be constructive. Instead of framing the investigation as an effort to find out who or what is at fault, management should instead take a more neutral approach. The investigation must focus more on what exactly happened, which system failure occurred, and what the company can do to prevent the incident from happening again. 

When should incident investigations occur?

Employees must report incidents very soon after they occur, and employers must conduct incident investigations in a timely manner.

The timeliness of reporting and investigating is crucial. If an employee reports an incident weeks after it occurred, it can have an impact on the investigation. Witnesses may forget crucial details after some time and physical evidence may already be tampered with. Not only can this prolong the investigation, but it can also affect the accuracy of the outcome.

Part 2: Incident Investigation Principles

Use the Correct Terms

Using the correct words and terms during an investigation can help ensure that employers, management, and employees are in the right frame of mind. These particular terms are important when conducting a workplace incident investigation:

Incident vs Accident

OSHA previously used the word “accident” to refer to fatalities, injuries, illnesses, and close calls that happen in the workplace. However, “incident” has since replaced “accident.” This is because describing an event as an “accident” makes it seem like the event is unpreventable. However, most of these events are preventable. Thus, the term “incident” is considered to be more accurate.

Close Call or Near Miss

A close call or a near miss is an event that almost caused an injury but did not. Going back to the case study, a close call is when the employee was able to dodge the machine’s moving parts. In this situation, the employee was just a few inches out of the reach of the moving parts and was, therefore, able to walk away unscathed.

Root Causes

Root causes are oftentimes not the immediately observable cause of an incident. If an employee is struck by a machine’s moving part and gets injured as a result, the root cause of the incident is not the machine’s moving part. The root cause is likely a system failure — managerial, organizational, or operational failings that led to the conditions that eventually caused the injury.

Surface Causes

Surface causes are specific hazards or behaviors. These include personnel errors, insufficient maintenance, hazardous environments, and the like. In the case study, the surface cause is the employee getting too close to the machine’s moving parts.

Direct Causes

Direct causes are the results of behaviors and/or physical contact with certain hazards. In the case study, the direct cause of the injury is the machine’s moving part, which then struck and injured the employee.

Investigate All Incidents

If an incident resulted only in a very minor injury, or if it was just a close call, management will still have to conduct a proper investigation. Maybe this time the outcome of the incident wasn’t so bad, but next time it could be worse.

Thus, it’s important to identify possible ways to prevent similar incidents in the future. Incident investigations are not just retroactive; they are also a proactive way of preventing injuries and dealing with workplace hazards.

Follow the Systems Approach

One important principle to remember is that incident investigations focus on systems, not behaviors. Going back to the case study, it can be easy to conclude that the incident occurred because the employee got too close to the machine and was unable to avoid its moving parts.

By focusing on individual behaviors, the investigation will:

  • Assign blame, which can be counterproductive and affect employees’ cooperation with the investigation

  • Not be able to identify any measures that employers and employees can take to prevent future incidents

Using the systems approach is more productive and avoids the assignation of the blame to specific individuals. With the case study, the systems approach will lead the investigation to identify actionable system failures that led to the employee’s injury. The possible system failures in this example can be defective equipment, lack of training, poor surface maintenance, or failure to eliminate identified hazards.

Focus on Root Causes

Incident investigation root cause analysis identifies 6 categories of system failures, also known as root causes. These are:

  • Materials

  • Machine/Equipment

  • Environment

  • Man

  • Methods

  • Management System

Dealing with the surface causes of an incident without getting to the root cause of the issue is a band-aid solution. Simply reminding employees to be careful when performing maintenance on machines, for example, deals with the issue on a surface level. Mistakes can still happen in the future, and the problem will continue.

The root cause of the problem in the case study is the absence of an effective lockout tagout program that will protect employees. The employer also needs to invest in durable lockout tagout devices, such as valve locks or circuit breaker locks. By recognizing this, the employer will be able to take the necessary steps to protect employees from injury in the future.

Identifying the root cause and focusing on it instead makes it more unlikely for the incident to happen again. This is a more constructive approach that improves workplace safety and employee morale all at once.

Part 3: The 4-Step Systems Approach

infographic of incident investigation kit

Preserve/Document the Scene

Once an incident has occurred, prevent access to the area. This will prevent physical evidence from being removed or tampered with. Once investigators preserve the scene, they will have to document the facts of the incident.

There are a few tools that investigators use to document a scene. These include:

  • An OSHA incident investigation form

  • An incident investigation kit

  • Cameras for taking videos and photos

  • Pencils and papers for sketching the scene

incident investigation collecting information

Cameras are useful in documenting the scene of an incident.

Collect Information

Investigators should have an incident investigation checklist to ensure that they collect as much information as possible. This checklist should include ways to find details such as the identities of the persons involved in the incident, the location of the incident, the supervisor in charge at the time of the incident, and so on.

Interviews are often a highly effective way to collect information. The incident investigation interview questions should therefore be as detailed as possible and should be formulated to help the investigator arrive at the root cause of the incident.

However, the timing of interviews is crucial. This is why an OSHA incident investigation must happen in a certain time frame. Investigators need to conduct interviews while memories are still fresh. It’s best to conduct the interview very soon after an incident has occurred, ideally right after the area is deemed safe. This way, the information the witnesses provide during the interviews is more likely to be accurate and detailed.

Investigators can also peruse various documents for more information. These documents include:

  • Manuals

  • Company policies and records

  • Reports

  • Maintenance schedules

  • Audits

  • Recommendations for corrective actions 

Determine the Root Causes

The previous discussion on root causes above was more about why it’s important to identify system failures in incident investigations. This discussion focuses more on how to determine the root causes of an incident.

Determining the root cause of an incident entails pursuing a logical line of thought and repeatedly asking why things occurred the way they occurred.

Take again the circumstances in the case study. These are some questions that an investigator might ask in this situation:

  • Was there a failure in following cleaning and maintenance procedures? If so, why?

  • Was there any incentivizing deviation from established procedures, such as the faster completion of tasks? If so, why has this problem not been previously identified?

  • Are there any alternative measures instead of lockout tagout that can help safeguard employees against the machines’ moving parts? If so, were these alternative measures put in place?

  • Are these alternative measures sufficient in protecting employees against injury? In what ways can they be improved?

  • Was there a failure to properly identify and/or report issues with the established cleaning procedures? If so, why?

Answers like “the employee failed to take alternative protective measures,” or “the employee was standing in the way of the moving part” is insufficient. Thorough investigations involve digging more deeply into these answers to find the root cause of the problem.

This line of questioning will lead to the root cause, which can then lead to solutions that will prevent the problem from recurring.

Implement Corrective Actions

Once the root cause has been identified, the company has to take corrective actions. These actions have to directly address the root cause and should not be band-aid solutions. 

For example, marking a spot on the floor where employees should stand when cleaning the machine can help them stay out of the way of moving parts. However, it does not address the root cause of the issue and it will not effectively prevent future injuries.

While corrective actions can directly address issues that contribute to the occurrence of worksite incidents, corrective actions can also be more general. Corrective actions like these can take the form of changes in policies, developing new safety programs, changing inspection procedures, and the like.

Part 4: Final Steps

Recommending Improvements and Corrective Actions

Recommending changes that a company has to make to improve workplace safety is an important part of an incident investigation procedure. These recommendations should be focused on the following:

Engineering Controls

Engineering controls are measures and solutions that protect employees from hazards by eliminating or reducing hazardous conditions. Some examples include ventilation systems, barriers, containment of hazardous materials, and the like.

Management Controls

Management controls seek to protect employees from hazards by regulating and modifying behaviors. One example of this is the use of lockout tagout devices, which can help prevent employees from operating machines that are under maintenance or servicing.

While these solutions are important in the workplace, it’s important to remember that management should not rely on management controls alone to maintain workplace safety.

Temporary Measures

Temporary measures are quick fixes that will suffice in the meantime, but not for long. These measures lend the company more time to develop more long-lasting solutions while keeping employees safe from hazards.

Incident Investigation Report

Who fills out the incident investigation report? Once the investigation is over, investigators will have to write a report on their findings. A complete incident report includes the following parts:


This section includes the name of the victim and the details of the witnesses to the incident, such as their names, address and contact details, job titles, and length of service. The background also includes the date and time of the incident, the date and time that the incident was reported, and where the incident occurred.

Description of the Accident

In this section, the investigator has to describe how the incident unfolded, including the details of relevant events that occurred before, during, and after the incident.

Findings and Justifications

The investigator has to describe the surface and root causes of the incident. In the case study, the investigator can write that the surface cause is the employee standing in the wrong place while cleaning the machine. The root cause, meanwhile, is the absence of lockout tagout.

This section will also have to include justifications for the findings, in which the investigator presents any proof of their findings.

Recommendations and Results

The investigator also has to include any corrective actions taken by the company. These include actions that address surface as well as root causes. Thus, the investigator will have to describe any actions that seek to eliminate hazards as well as any revisions or additions to programs and procedures.


This section details the estimated costs of the incident, as well as the amount that the company will have to invest in corrective actions.


At the end of the report, the investigator has to describe corrective actions and system improvements taken by the company, as well as the individuals responsible for these measures. The investigator also has to identify any individuals responsible for following up on the said actions and improvements.

OSHA incident investigation reports are often considered to be open documents until management takes all corrective actions to address the incident. However, even when the matter is closed, companies will still have to periodically assess and evaluate their incident investigation techniques and the effectiveness of the actions they implemented.


The material provided in this article is for general information purposes only. It is not intended to replace professional/legal advice or substitute government regulations, industry standards, or other requirements specific to any business/activity. While we made sure to provide accurate and reliable information, we make no representation that the details or sources are up-to-date, complete or remain available. Readers should consult with an industrial safety expert, qualified professional, or attorney for any specific concerns and questions.


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Author: Herbert Post

Born in the Philadelphia area and raised in Houston by a family who was predominately employed in heavy manufacturing. Herb took a liking to factory processes and later safety compliance where he has spent the last 13 years facilitating best practices and teaching updated regulations. He is married with two children and a St Bernard named Jose. Herb is a self-described compliance geek. When he isn’t studying safety reports and regulatory interpretations he enjoys racquetball and watching his favorite football team, the Dallas Cowboys.