Most workers have seen something go wrong on the job. Someone slips but catches themselves. A tool or material falls but misses a worker. Equipment fails and causes damage but no injury. Other times, someone does get hurt. Each event can provide clues about hazards that could cause another — perhaps more serious — incident.
That is why employers should investigate workplace incidents that cause injury, illness, property damage, or other loss, as well as close calls (sometimes called near misses). A good investigation looks for cause, not fault. Instead of stopping at “worker error,” investigators look deeper for problems with equipment, training, procedures, communication, supervision, maintenance, or other workplace systems. Finding and correcting these root causes can prevent future injuries and strengthen the entire safety and health program.
Follow these eight steps for an effective incident investigation.
1 Respond to the emergency and secure the area.
Help injured workers first. Call emergency medical services when needed. Then control immediate hazards by shutting down equipment, stopping leaks, de-energizing machinery, or restricting access. Never place yourself in a dangerous location or position when conducting an incident investigation. Protect the scene from unnecessary disturbance. Preserving equipment, materials, debris, controls, and other evidence can help investigators determine what happened.
2 Start the investigation quickly.
Begin as soon as conditions allow. Evidence can disappear, equipment can move, and people can forget important details. Prepare before an incident occurs by deciding who will investigate and making sure they know the procedures and resources they will need. When possible, include both management and employees who know the work. Bring in technical experts when specialized knowledge is needed. Investigating close-call incidents may expose hazards before someone gets hurt.
3 Document the scene and gather the facts.
Take photos or video of the overall area and important evidence from different angles. When possible, capture the location and orientation of vehicles, equipment, and other objects before they are moved. Use sketches and measurements to show where people and evidence were located and document tire or skid marks when vehicles or mobile equipment are involved. Record the date, time, work underway, equipment involved, and conditions that may have contributed to the incident.
Review training records, work procedures, maintenance and repair logs, equipment manuals, inspection reports, job hazard analyses, work permits, and records of previous incidents involving the same equipment or hazards. For vehicle or mobile equipment incidents, review pre- and post-trip inspection forms and consider whether work, rest, or driving times indicate that fatigue may have played a role. Focus on facts rather than assumptions.
4 Interview the people involved.
Talk privately and separately with injured workers, witnesses, and others familiar with the job. Explain that the investigation aims to prevent another incident, not assign blame. Ask open-ended questions such as “What did you see?” “What happened next?” and “What seemed different that day?” Give workers time to describe events in their own words without interrupting or suggesting answers.
5 Build a timeline.
Put the events in order and work backward to the last normal work activity. Look for changes in equipment, staffing, procedures, materials, workload, weather, or the work environment. Ask what changed, when it changed, and how that change affected the work. A clear timeline can uncover connections that investigators might otherwise miss.
6 Dig past the immediate cause.
Finding what directly caused an incident does not always explain why it happened. Suppose a worker slips on oil. Cleaning the spill fixes the immediate hazard, but investigators should ask more questions: Where did the oil come from? Why did the leak occur? Why didn’t anyone find or repair it earlier? Did the inspection or maintenance process fail?
Keep asking questions until you identify the contributing factors and underlying problems that allowed the incident to occur. An incident may have more than one contributing factor or root cause.
7 Correct the causes, not just the symptoms.
Choose corrective actions for each root and contributing cause. Whenever possible, eliminate the hazard or use engineering or other controls that reduce the risk without relying solely on workers remembering a rule. Corrective actions might include repairing equipment, improving maintenance, redesigning a task, updating procedures, changing work practices, or providing training. Training can support other controls, but training alone may not correct an equipment, maintenance, staffing, or other workplace-system problem. Assign responsibility for each action and set a completion date.
8 Share what you learned and follow up.
Document what happened, the contributing factors and root causes, and the corrective actions. Share useful lessons with employees and other work areas that may face similar hazards without blaming individuals. Then track corrective actions to completion and check whether they reduced the risk.
Periodically review incident and near-miss reports for patterns and look for similar hazards in other tasks or work areas. Use what you learn to improve training, procedures, inspections, maintenance, and other parts of your safety and health program.
Learn how to investigate workplace incidents
Want to strengthen your incident investigation skills? Register for DWC’s upcoming free Incident Investigation webinar to learn practical ways to gather facts, identify contributing factors and root causes, and develop corrective actions that can help prevent future injuries.
You can also download DWC's free Incident Investigation Safety Training Program, available in English and Spanish. This publication provides more detailed guidance, sample questions, investigation tools, OSHA reporting information, review questions, and practical steps for putting an incident investigation process into place.