What Is a Hazard?

A hazard is a condition, object, activity, or situation that has the potential to cause harm to people, property, or the environment. In safety engineering and risk management, the term is used precisely: a hazard is a source of potential harm, distinct from the risk it generates, which depends on both the likelihood of that harm occurring and its severity. This distinction, formalized in ISO/IEC Guide 51, is the conceptual foundation of most engineering safety frameworks.

Hazard identification and analysis draw from many disciplines: chemical and process engineering, systems safety, reliability theory, occupational health, and environmental science. In complex engineered systems, hazards arise from material properties, energy states, human factors, and the interactions among components that individually appear safe.

Types of Hazards

Hazards are generally classified by origin and mechanism. Physical hazards include stored mechanical energy, electrical faults, extreme temperature or pressure, and ionizing radiation. Chemical hazards involve flammable, toxic, corrosive, or reactive substances that can injure workers or contaminate environments. Biological hazards relate to pathogens, allergens, and other organisms capable of causing illness. Ergonomic hazards, sometimes overlooked in technical disciplines, arise from equipment or workflow designs that strain the human body over time.

In civil and industrial engineering, a further distinction is drawn between natural hazards, such as earthquakes, floods, and wildfires, and technological or man-made hazards arising from infrastructure failure, chemical spills, or industrial accidents. The UNDRR hazard definition and classification review documents the international taxonomy used in disaster risk reduction frameworks, which spans both categories.

Hazard Identification and Risk Assessment

Hazard identification is the first formal step in any structured safety program. Methods include systematic reviews such as the Hazard and Operability Study (HAZOP), Failure Modes and Effects Analysis (FMEA), and What-If analysis. Each method applies a different interrogation structure to a system design or process flow. The goal is to surface hazards before they contribute to incidents rather than after.

Once identified, hazards are characterized by their severity (the magnitude of potential harm) and probability of occurrence, producing a risk estimate. The IEC functional safety standard 61508 defines Safety Integrity Levels (SILs) that map acceptable risk thresholds to required risk-reduction measures for electrical and electronic systems.

Hazard Control

Engineering controls are the preferred means of addressing identified hazards because they reduce risk regardless of human behavior. Substitution, which replaces a hazardous material or process with a less hazardous one, provides the most reliable risk reduction. Elimination of the hazard source is preferred where operationally feasible. When hazards cannot be eliminated or substituted, engineering solutions such as interlocks, guards, and pressure relief valves provide barriers. Administrative controls, including procedures, permits, and training, form a secondary layer. Personal protective equipment sits at the end of the hierarchy and provides the least reliable protection.

The IEEE Public Safety Technology program addresses hazard control in contexts from fire protection to industrial automation, recognizing that rigorous hazard analysis reduces both human harm and economic loss from accidents.

Applications

Hazard analysis and control have applications in a wide range of engineering and societal contexts, including:

• Industrial process and plant safety
• Fire prevention and suppression system design
• Transportation infrastructure risk assessment
• Occupational health and workplace safety programs
• Environmental impact assessment for industrial projects
• Emergency response planning for natural and technological disasters