Workplace accident investigation and root cause analysis (RCA): 5 Why, Ishikawa diagram and CAPA

After an accident, first aid and securing the scene come first, to prevent further injuries and preserve evidence. The employer then appoints an investigation team that establishes circumstances and causes and prepares a report — in Poland, as a rule, within 14 days of being notified of the accident.

The team inspects the scene, collects statements from the injured person and witnesses, gathers documentation (photos, sketches, instructions, inspection records, training, medical examinations) and proposes preventive measures. Always check current regulations for formal requirements — this guide is not legal advice.

For every serious accident there are many minor injuries and even more near misses. They are the cheapest source of knowledge: nobody was hurt, people speak more openly and the causes are often the same as in serious events.

There is one condition — reporting must be simple and safe for the reporter. A QR code at the machine, a one-minute phone report, optional anonymity and feedback on what was done increase reporting more than any campaign.

5 Why means asking “why?” until the answer points to a gap in the system rather than one person's behaviour. Five is a guideline — sometimes three questions are enough, sometimes seven are needed.

Rules: start from a concrete fact, not a judgement; confirm each answer with evidence (photo, record, interview); branch the analysis when several causes appear; stop when you reach a cause the organisation controls and can remove with an action that has an owner and a deadline.

The most common mistake is stopping at “human error”. Asking “why was the worker in a hurry?” usually leads to work planning, shift staffing or a missing instruction — and that is where the root cause lies.

The Ishikawa diagram structures team brainstorming. The effect goes in the “fish head” and possible causes are grouped into categories: Man, Machine, Method, Material, Environment — often with a sixth category, Management or Measurement.

It works well when there may be many causes and the team needs a broad view before focusing on one hypothesis. Combining methods gives the best results: Ishikawa shows possible causes and 5 Why digs into the ones confirmed by evidence.

An analysis without actions is just a document. Every confirmed root cause should have a corrective action (removes the cause) and, where it makes sense, a preventive one (applies the lesson to similar places, e.g. all platforms on site).

A good action has an owner, a deadline and an effectiveness criterion. After implementation, check that it worked and update the workstation risk assessment, instructions and training. The hierarchy of controls applies: elimination and engineering before administrative controls, PPE last.

Looking for someone to blame instead of a cause; “instruct the worker” as the only action; no evidence for successive answers; investigating too late, when evidence is gone; actions without owner and deadline; no effectiveness check; ignoring near misses.

In VIMS an incident or hazard report can be sent from a phone, including via a QR code, with photos and location. The accident and incident register follows the case from report through team documentation to close-out.

The root cause analysis module lets you run 5 Why and Ishikawa directly on the incident and turn conclusions into CAPA tasks with owner, deadline and effectiveness review. An incident can also flag that a workstation risk assessment needs review.

Workplace accident — under Polish law (Act of 30 October 2002, Art. 3): a sudden event caused by an external factor, resulting in injury or death, connected with work. If any element is missing, the event is not a workplace accident.

Serious, fatal and multiple accidents — a serious accident causes grave bodily harm, a fatal one death within 6 months, a multiple one affects at least two people. The employer must notify the labour inspectorate and prosecutor without delay (Labour Code Art. 234 § 2).

Commuting accident — a separate category recorded on a commuting accident card, not in the workplace accident register.

Investigation team and accident report — the team (usually the OHS specialist and a worker representative) establishes circumstances and causes and issues the report within 14 days of notification. The accident is then entered in the accident register and a statistical card goes to Statistics Poland (Z-KW).

Technical, organisational and human causes — the classification used in reports and statistics. A human cause is rarely the root cause; it usually points to missing guarding, supervision or an unclear instruction.

Ishikawa 5M+E — diagram branches: man, machine, method, material, measurement and environment. They stop the team at the first obvious cause.

Heinrich and Bird pyramid — a model in which one serious accident sits on many minor injuries and hundreds of near misses. The ratios are illustrative, but the lesson holds: near miss reporting lets you act before injury.

Accident frequency rate and LTIFR — Statistics Poland reports injured persons per 1,000 employed; international reporting uses LTIFR, lost-time injuries per million hours worked.