Accident and occupational disease investigations are done to determine the causes of physical injuries and occupational diseases. They are also undertaken to satisfy the legal requirements of health and safety legislation.

But for CUPE members, there is more to investigations than this. Investigations should also be used to uncover workplace problems, eliminate workplace hazards and strengthen workplace health and safety programs. Investigations can also provide information to back up workers’ compensation claims.

CUPE members shouldn’t wait for an accident or a disease to conduct an investigation. Near misses, health and safety incidents and complaints are signs that an accident or disease might be just around the corner. These should also be investigated to expose workplace hazards. Investigations must always focus on the root causes of the hazard.

The joint health and safety committee must play a leading role to uncover the hazards that led to the accident, disease or incident.

Usually, legislation requires that critical injuries and fatalities be investigated. Legislation in most jurisdictions stipulates that worker members of a joint health and safety committee investigate critical injuries and fatalities or be informed when they happen.

Health and safety legislation differentiates an accident from an incident. An accident is defined as an unplanned event that interrupts a work activity and that may or may not include injury. An incident is defined as an unplanned event that involves no physical injury. An incident and a near miss are basically the same thing.

What happens before an accident investigation?

A joint health and safety committee should form an investigation team as part of their normal activities. This will ensure that an investigation will be conducted properly and efficiently if there is a need. Unions can have their own investigation team. Some CUPE locals have won the right to conduct union-only investigations. No matter who is in charge of investigations, CUPE members must be equal participants. Some jurisdictions require investigations be conducted jointly by the employer and workers.

CUPE investigators must be trained and ready ahead of time. A written investigation action plan or checklist must be in place.

The supervisor working where the accident took place should not be part of the investigation team. There could be an attempt to cover up the supervisor’s errors that led to the accident.

Investigations must always have a broad perspective on what led to the accident or incident. Investigations should never jump to quick conclusions, such as simply blaming the worker for what occurred.

What do you do if an accident happens?

The first people on the scene of an accident or incident must deal with the immediate problems. If the injured person needs medical attention, call an appropriate medical professional. The accident or incident must also be reported immediately to a supervisor or appropriate person at the workplace. Once the injured person is looked after, take a quick look at the site and see that nothing be moved or tampered with unless it is necessary to attend to injured persons or to prevent further injuries. Make sure all witnesses are identified.

Next, stop work, shut down equipment, seal the area off if necessary and follow established procedures. In some jurisdictions, nothing may be touched until a government inspector arrives. Inspectors and police have the right to collect and remove samples and equipment for analysis. If this happens, make note of it in the investigation report. Document what was removed and the location from where it was taken.

The investigation team must be ready to perform its duties. An investigation kit should be prepared ahead of time that contains:

  • A camera to photograph evidence.
  • Tape measure.
  • Pads of paper and pens.
  • Investigation checklist.
  • Flashlight with extra batteries.
  • Audiotape and/or video recorder.
  • Clear plastic bags to collect and protect physical evidence.
  • Protective gloves, HEPA masks and eye protection.

Before starting any investigation, first preserve physical evidence on the scene. Next, record the appearance of the scene with photographs, diagrams and written notes.

How do you collect information?

An investigation can begin once the scene has been recorded and the area secured. Try to start the investigation as soon as possible after the accident or near miss.

Investigators should ask and then discuss the following questions:

  • What happened?
  • Where did the accident happen?
  • When did the accident happen?
  • When was it noted and reported?
  • How did the accident happen?
  • Who is injured?
  • Who are the witnesses?
  • Who else was in the vicinity of the accident?
  • What equipment, machinery, chemicals, work processes and manual materials handling was involved?
  • What conditions changed as the work was being done and the accident happened?
  • What else was going on in the workplace as the accident happened?
  • What were the weather and/or traffic conditions?
  • What was the behaviour of the client or patient?
  • Why did things happen?
  • Why did things not happen?

The investigation team should record all of the information that comes from answering these questions. Investigators must uncover all sources of information. This means information should be gathered from:

  • Injured workers
  • Eyewitnesses
  • Physical evidence
  • Background information

Injured workers

An injured worker is a crucial information source. Interviewing an injured worker at the scene can sometimes be impossible, due to their physical and mental state. If a worker is too upset or too injured to be interviewed, you must hold off on interviewing until the worker has recovered.


Eyewitness accounts are also vital. Witnesses are usually under varying amounts of stress due to the trauma experienced by seeing an accident or a near miss. Sometimes when a witness is upset, it is the investigator who must calm down the witness.

Investigators need to ask witnesses the following questions:

  • When did you notice the accident had taken place?
  • Where were you when you noticed the accident?
  • What activity were you doing when the accident happened?
  • What were the physical conditions (e.g., temperature, lighting, weather, etc.) at the time of the accident?
  • What did you see? What sounds did you hear?
  • Was there anything unusual in the workplace when the accident happened?
  • What do you think caused the accident?
  • Are there any other factors you think are important to the investigation?

Do not interrupt the witness or get emotional during the interview. Record all interviews with an audiotape or video recorder to avoid taking notes while listening to a witness. Make sure to first get the witness’ permission to record her/him.

Physical evidence

Investigators should take an inventory of physical evidence (i.e., materials and equipment) around the accident site. Look for:

  • Any broken or altered equipment and missing parts.
  • The condition of safety devices, guards and controls.
  • The location and condition of physical barriers that separate workers and the public.
  • The cleanliness of the accident site.
  • Poor lighting, any blind spots or poor sight lines.
  • Noise hazards around the accident site.
  • Chemical hazards around the accident site.
  • Where the injured workers are (or were) located.

Again, record this information with notes, diagrams and photographs.

Background information

Investigators also need to examine relevant background information. This includes information such as past accident reports, workplace inspections, training materials and maintenance records. This information might show unsafe conditions, accidents or near misses. These records can give investigators information to help identify causes and act to prevent further accidents. Investigators should be able to identify what caused the accident by combining all of the information from these different sources.

What happens after the information is collected?

A report on the accident must be written. The report describes what happened and what caused the accident.

Recommendations should also be presented in the report. Recommendations should be specific and have timelines for corrective measures. For example, if the accident happened because there wasn’t enough light to see the controls on a piece of machinery, the recommendations need to address the hazard directly. In this example, recommendations could start by suggesting:

  • Proper and adequate lighting to be installed to light all controls on all machinery within three days of the submission of this report.
  • Check lighting levels throughout the workplace. If poor lighting exists in other areas, it must be corrected within two weeks of the submission of this report.
  • Corrective measures to lighting levels must be done in consultation with CUPE members.

The written report needs to be thorough and state basic facts such as the “who, what, when, where, why and how” of the accident. Sections can be divided into Injured Worker Account, Physical Evidence, Eyewitnesses, Photographs and Drawings, Background Information and Recommendations. Often workplace health and safety committees have standard forms for accident investigations. If forms are too short, do not hesitate to attach information. The investigation report must be as detailed as possible to be effective in helping prevent future accidents or incidents.

The written report should be presented and discussed at a joint health and safety committee meeting and a union health and safety committee meeting. The recommendations should be tabled and the necessary changes made in the workplace. Follow-up work is also needed. The recommendations and changes that come out of an accident investigation must be monitored to see if they are working.

To summarize, the major steps for an accident investigation are:

  • Form an investigation team.
  • Report the accident to a designated person on the health and safety committee and to a supervisor.
  • Give first aid to the injured worker(s).
  • Start the investigation as soon as possible after the accident.
  • Identify the causes.
  • Report the findings and recommendations to the health and safety committee.
  • Develop a plan for improvement of the working conditions that led to the accident.
  • Evaluate the plan.
  • Apply the plan.
  • Monitor the plan’s effectiveness.

Occupational disease investigations

An accident is usually clear to everyone and an accident investigation is usually automatic. By comparison, occupational disease is harder to determine and to investigate.

Unhealthy workplaces are familiar to many CUPE members. Toxic substances, poorly designed equipment and inadequate ventilation are just a few of the ongoing hazards that contribute to occupational diseases. Because the symptoms of some occupational diseases – like occupational cancers – take decades to appear, the link between work and disease may not be clear.

When workers get sick from occupational disease, they often do not suspect a connection between their work and their illness. For this reason, occupational disease investigations should be carried out. They can be useful to investigate complaints, reports of illness or disease, or to support workers’ compensation claims.

There are important differences between accident investigations and occupational disease investigations. Occupational disease investigations are not as straightforward because:

  • Accidents and their causes are usually much more visible and the connections between the two are more apparent.
  • Some occupational diseases are also communicable diseases that can be transmitted. This can complicate how the illness should be treated, tracked and prevented.
  • Work-related symptoms can be confused with common illnesses and disease symptoms.
  • Chronic (long-term) effects usually do not appear until many years after the first exposure.
  • Many health care professionals know little about the causes of occupational diseases. They may miss the connection between the workplace and the disease entirely.
  • Very little is known about the health effects of many substances found in workplaces. For example, custodians, hospital workers and municipal workers use more new and potentially toxic cleaners, solvents and chemicals. Most have not been thoroughly tested for their safety.
  • Showing a link between occupational disease and the workplace requires intensive research, interviews and surveys.

Occupational disease investigations often require the help of worker-friendly organizations that have the knowledge and tools necessary to carry out the investigation. The Occupational Health Clinics for Ontario Workers (OHCOW) is an example of an organization that can help workers with an occupational disease investigation.

For more information, consult the Accident and Occupational Disease Investigations Guideline produced by the National Health and Safety Branch or contact:

CUPE National Health and Safety Branch
1375 St-Laurent Boulevard

Tel: (613) 237-1590
Fax: (613) 237-5508