What is a hazard analysis?
A hazard analysis is the core of product and process safety risk management. It answers four questions: what can cause harm, how could someone be exposed, how bad and how likely is it, and what are we doing about it? It is required for medical devices (ISO 14971), machinery (ISO 12100), and functional safety (IEC 61508), and good practice for any product that can hurt someone. Failure modes found in an FMEA often feed the hazard analysis as causes of hazardous situations.
Hazard categories to consider
- Energy: electrical, mechanical (moving parts, pressure), thermal, radiation.
- Biological and chemical: infection, contamination, toxicity, biocompatibility.
- Use error: slips, lapses, mistakes, foreseeable misuse.
- Information and software: wrong data, unclear labels or alarms, software faults.
- Functional failure: loss or degradation of a function the user relies on.
Hazard analysis example
The example covers a volumetric infusion pump. Free flow of drug and a tenfold programming error both start as extreme risks (severity 5, probability 3). An automatic anti-free-flow clamp, an inherent safety by design control, reduces the free-flow risk to medium. The drug library with dose limits reduces the programming error only to high, because the severity stays catastrophic: this residual risk needs further reduction or a documented benefit-risk decision. The other hazards end at medium, each with its verification evidence.
ISO 14971 risk management
ISO 14971 requires a risk management plan, risk analysis, risk evaluation against acceptability criteria, risk control with verification, evaluation of overall residual risk, and production and post-production information that feeds back into the analysis. Complaint and nonconformance data should update the probability ratings over the product's life, which is where a connected QMS helps.
How to use this Hazard Analysis tool
- Define the scope. Describe the product or process, its intended use and the analysis team.
- Identify hazards. List hazards by category: energy, biological, chemical, use error, software and functional failure.
- Describe the chain. For each hazard, write the sequence of events, the hazardous situation and the harm.
- Estimate the risk. Rate severity and probability; the matrix shows the initial risk.
- Control and verify. Add risk controls, their type and the evidence of effectiveness, then rate the residual risk.
- Review and export. Check that every residual risk is acceptable and export the hazard analysis.
Frequently asked questions
What is a hazard analysis?
A hazard analysis systematically identifies the hazards of a product, process or system, how people or property could be exposed to them, and what harm could result. Each hazardous situation is rated for severity and probability, risk controls are defined, and the residual risk is evaluated.
What is the difference between a hazard, a hazardous situation and harm?
In ISO 14971 terms, a hazard is a potential source of harm (for example, electrical energy). A hazardous situation is a circumstance in which people are exposed to the hazard (a patient touching an enclosure with leakage current). Harm is the injury or damage that results (electric shock). A sequence of events links them.
In what order should risk controls be chosen?
ISO 14971 and ISO 12100 set a priority order: first inherent safety by design (remove or reduce the hazard), then protective measures in the product or process (guards, alarms, interlocks), and only then information for safety (warnings, labels, training). Information for safety alone rarely reduces the probability of harm much.
How do I verify the effectiveness of risk controls?
Each control needs objective evidence that it is implemented and that it works: design verification tests, usability (human factors) studies, inspection records or field data. Record the evidence in the verification column so the risk file is traceable.
How is this different from a preliminary hazard analysis?
A preliminary hazard analysis is done early in design, at system level, with limited information. A detailed hazard analysis follows the full chain from hazard to harm for the defined design, including verified controls and residual risk. Many teams start with a PHA and evolve it into the detailed hazard analysis.