How to identify hazards and hazardous situations
ISO 14971:2019 §5 — Risk analysis: hazard identification
The short answer
Hazard identification is the first step of risk analysis. You must systematically identify all hazards, sequences of events that could lead to hazardous situations, and the harms that could result. ISO 14971 Annex C provides a checklist of hazard categories as a starting point.
The hazard chain: from hazard to harm
ISO 14971:2019 defines a specific chain of causation that you must trace for each risk in your hazard log:
- Hazard — the potential source of harm (e.g., high-voltage supply in device housing)
- Sequence of events — the circumstances and foreseeable events that could expose someone to the hazard (e.g., insulation failure → exposed contacts → user touches device)
- Hazardous situation — the circumstance in which people are exposed to the hazard (e.g., user in contact with live voltage)
- Harm — the actual injury or damage (e.g., electric shock causing cardiac arrest)
Example hazard chain table
| Hazard | Sequence of events | Hazardous situation | Harm |
|---|---|---|---|
| High-voltage power supply | Insulation failure → exposed metal surface | Operator touches exposed contact during maintenance | Electric shock, cardiac arrest (Catastrophic) |
| Sharp cutting element | Misalignment during assembly → guard not seated | Clinician handles device without guard in place | Laceration (Serious) |
| Incorrect software output | Input data out of range → algorithm extrapolates → incorrect dose recommendation | Clinician acts on incorrect dosing recommendation | Over- or under-dosing (Critical) |
| Latex components | Patient with latex allergy contacts device | Allergic reaction during procedure | Anaphylaxis (Critical) |
| Biofilm formation | Inadequate cleaning → residual protein on surface | Reuse of inadequately cleaned device | Infection (Serious to Critical) |
Types of hazards (ISO 14971:2019 Annex C)
Annex C of ISO 14971:2019 provides an informative checklist of hazard categories. Your hazard analysis should demonstrate that you have considered each category:
- Energy hazards: electrical, thermal, mechanical, radiation (ionizing and non-ionizing), acoustic/vibration
- Biological hazards: biocompatibility, reinfection, microbial contamination, pyrogenicity
- Chemical hazards: leachables, degradation products, flammability, toxicology
- Information hazards: inadequate labelling, instructions for use, training requirements, inadequate software output
- Functional hazards: failure to perform intended function, incorrect output, data loss
- Environmental hazards: temperature extremes, humidity, EMI, altitude, transport and storage conditions
Hazard identification methods
Failure Mode and Effects Analysis (FMEA)
FMEA systematically considers how each component or function could fail (failure modes), what effects those failures would have on the system, and ultimately what harm could result. FMEA works well for hardware components and design-level analysis. ISO 14971 does not mandate FMEA but it is the most commonly used method in medical device risk management.
Fault Tree Analysis (FTA)
FTA is a top-down deductive technique that starts with a defined top-level hazardous event (e.g., "patient receives incorrect dose") and works backwards through logical AND/OR gates to identify all combinations of events that could cause it. FTA is particularly useful for complex systems where a single harm could arise from multiple different failure pathways.
Preliminary Hazard Analysis (PHA)
PHA is a broad initial scan performed early in design to identify all categories of hazard associated with a device concept before detailed design decisions are made. It is less rigorous than FMEA or FTA but is valuable for setting the scope of subsequent analyses.
HAZOP (Hazard and Operability Study)
Originally developed for process industries, HAZOP applies a set of guide words (No, More, Less, As Well As, Other Than, Early, Late, Before, After) to each design parameter or process step to identify deviations and their consequences. Useful for analysing infusion pump programmable functions and surgical device workflows.
Foreseeable misuse
ISO 14971:2019 §5.4 requires you to consider reasonably foreseeable misuse — not just the intended use. This includes:
- Use by untrained or inexperienced users
- Use outside the labelled patient population (e.g., paediatric patients on adult device)
- Use in environments outside specified conditions (e.g., operating in high humidity)
- Modification or repair by users or third parties
- Single-use devices reused or reprocessed
- Device used with incompatible accessories or consumables
Documenting hazard identification
The output of hazard identification must be documented in the Risk Management File (§4.5). Typical documents include:
- Hazard register / hazard log listing all identified hazards
- FMEA worksheet with failure modes, effects, and initial risk estimates
- Annex C coverage table demonstrating all hazard categories were considered
- Intended use and reasonably foreseeable misuse description