NEBOSH Incident Investigation 3 — Questions and Answers
Question 1: What immediate and underlying causes might be identified when investigating a worker who fell from a ladder?
- Immediate: the worker was clumsy; Underlying: they should not have been hired
- Immediate: the ladder was damaged/improperly positioned; Underlying: lack of ladder inspection regime, inadequate work-at-height risk assessment, or insufficient training in ladder use (Correct answer)
- Immediate: the floor was too hard; Underlying: the building was old
- Immediate: the worker fell; Underlying: gravity exists
Correct answer: Immediate: the ladder was damaged/improperly positioned; Underlying: lack of ladder inspection regime, inadequate work-at-height risk assessment, or insufficient training in ladder use
A thorough investigation distinguishes between immediate causes (the direct physical events — damaged equipment, poor positioning) and underlying causes (the management system failures — no inspection programme, inadequate risk assessment, poor training). Addressing only immediate causes treats symptoms; root cause analysis addresses the systemic failures that allowed the situation to develop.
Question 2: Under RIDDOR 2013, what constitutes an 'over-7-day incapacitation' that must be reported?
- Any illness lasting more than 7 days
- When a worker is incapacitated for more than 7 consecutive days (not counting the day of the accident) from carrying out their normal work duties as a result of a work-related injury (Correct answer)
- When a worker takes more than 7 sick days in a year
- Any absence exceeding 7 days for any reason
Correct answer: When a worker is incapacitated for more than 7 consecutive days (not counting the day of the accident) from carrying out their normal work duties as a result of a work-related injury
An over-7-day incapacitation is reportable when a worker is unable to carry out their normal work duties for more than 7 consecutive days (excluding the day of the accident) as a result of a work-related injury. This must be reported within 15 days of the accident. The incapacitation does not have to be absence from work — inability to do normal duties is sufficient.
Question 3: How does the Swiss cheese model explain why multiple safety barriers sometimes fail simultaneously?
- Because all safety barriers are equally unreliable
- Because each defensive layer has latent weaknesses (holes) that are normally offset by other layers, but organisational factors, complacency, or unusual conditions can cause the holes to align temporarily, allowing a hazard to penetrate all defences (Correct answer)
- Because safety barriers are never properly maintained
- Because regulations do not require enough safety barriers
Correct answer: Because each defensive layer has latent weaknesses (holes) that are normally offset by other layers, but organisational factors, complacency, or unusual conditions can cause the holes to align temporarily, allowing a hazard to penetrate all defences
Each layer of defence has latent conditions (dormant weaknesses) created by organisational factors such as time pressure, budget cuts, poor communication, or inadequate training. Normally, even if one layer fails, others catch the hazard. But when organisational pressures or unusual circumstances cause multiple weaknesses to align simultaneously, the hazard passes through all layers.
Question 4: What type of evidence should be gathered during an accident investigation?
- Only witness statements are needed
- Physical evidence (scene preservation, photographs, equipment), documentary evidence (procedures, training records, risk assessments, maintenance logs), and testimonial evidence (witness statements, expert opinions) (Correct answer)
- Only the injured person's account of what happened
- Only CCTV footage if available
Correct answer: Physical evidence (scene preservation, photographs, equipment), documentary evidence (procedures, training records, risk assessments, maintenance logs), and testimonial evidence (witness statements, expert opinions)
A thorough investigation gathers three types of evidence: physical (preserving and photographing the scene, examining equipment, collecting samples), documentary (reviewing relevant procedures, training records, risk assessments, maintenance records, previous incident reports), and testimonial (interviewing witnesses, the injured party, supervisors, and consulting technical experts).
Question 5: In a 5 Whys analysis, a worker suffered a chemical burn. The sequence revealed: Why burned? No gloves worn. Why no gloves? None available. Why none available? Not ordered. Why not ordered? No reorder system. Why no system? No one assigned responsibility. What is the root cause?
- The worker was negligent for not wearing gloves
- A management system failure — no one was assigned responsibility for maintaining PPE stock levels, meaning there was no system to ensure availability (Correct answer)
- The chemical was too dangerous to use
- The purchasing department was understaffed
Correct answer: A management system failure — no one was assigned responsibility for maintaining PPE stock levels, meaning there was no system to ensure availability
The 5 Whys traced the cause from the immediate event (burn) through proximate causes (no gloves, none available, not ordered) to the root cause: a management system failure where responsibility for maintaining PPE stock was never assigned. This root cause is actionable — assigning responsibility and implementing a reorder system prevents recurrence.
Question 6: What is the purpose of a RIDDOR report from the perspective of the enforcing authority?
- To generate revenue through reporting fees
- To enable the enforcing authority to identify patterns and trends, target inspection and enforcement activity, and investigate serious incidents to establish whether health and safety law has been breached (Correct answer)
- To create a database for academic research only
- To calculate the employer's insurance premium
Correct answer: To enable the enforcing authority to identify patterns and trends, target inspection and enforcement activity, and investigate serious incidents to establish whether health and safety law has been breached
RIDDOR reports provide the HSE and local authorities with intelligence about workplace injuries, diseases, and dangerous occurrences. This data enables them to identify sectors, hazards, and trends where intervention is most needed, target inspection resources effectively, investigate individual incidents where necessary, and monitor the overall effectiveness of health and safety regulation.
NEBOSH Incident Investigation 3
What immediate and underlying causes might be identified when investigating a worker who fell from a ladder?