How do you investigate a workplace accident?

An investigation should lead to better controls

The purpose is to understand what allowed the event and prevent further harm. A report that ends with “be more careful” may leave the same equipment, pressures or unclear arrangements in place.

HSE’s investigation workbook sets out gathering information, analysis, control measures and an action plan. This guide uses that practical method; it does not replace a regulator, police or other official investigation or decide individual liability.

1. Make the response safe and organise the investigation

Arrange the appropriate immediate response, prevent further exposure and follow any official instructions about the scene or evidence. Do not put someone at risk simply to preserve a photograph.

• Choose people with the knowledge and authority needed for the incident.
• Clarify the investigation’s scope, including affected work and people.
• Check reporting duties promptly and separately from the investigation.
• Identify records, equipment, accounts and other evidence that may be lost.

HSE’s reporting guidance helps identify the responsible person for a GB statutory report. An investigation is not a reason to miss a reporting deadline; Northern Ireland has separate reporting arrangements.

2. Establish facts before explaining causes

Record what is known, its source and what still needs checking. Speak to people promptly and respectfully, using open questions about the work rather than supplying an answer. Distinguish an observation from an assumption.

Keep personal information appropriately controlled and share investigation material through the business’s authorised arrangements.

3. Build a chronology and test explanations

Hypothetical example. A worker trips over packaging left beside a packing bench. The chronology finds that packaging disposal was delayed when a container became full, no replacement was available and the temporary storage area obstructed the route.

“The worker did not look” does not explain those conditions. Investigate the disposal arrangement, resources, route and response to a full container as well as the worker’s actions. Check competing explanations against the evidence rather than stopping at the first plausible story.

HSE’s workbook distinguishes immediate, underlying and root causes. Those labels help organise the explanation; they do not mean every event has one simple root cause.

4. Assign controls and verify the result

Give each action an owner and completion point. HSE’s management guidance emphasises using monitoring and lessons to improve arrangements. Closing an action requires checking what changed in practice, not simply marking a form complete.

Common mistakes that weaken the findings

• Beginning with blame. It can hide the conditions that made the event possible.
• Treating assumptions as facts. Record uncertainties and test them.
• Only investigating injuries. A near miss may reveal a serious control weakness.
• Choosing retraining for every cause. Equipment, layout or resources may need changing.
• No follow-up. Check that actions work and share the relevant learning with affected people.

Next steps

1. Address immediate risks and official evidence needs.
2. Gather facts and build a clear chronology.
3. Test explanations and identify the controls that need improvement.
4. Assign, verify and communicate corrective actions.

Open HSE’s investigation workbook — Provides the regulator’s structured investigation method and supporting tools.