Any threat to personal safety should be regarded as a hazard and treated as such. This article discusses threats from several sources, such as kinematic/mechanical hazards, electrical hazards, energy hazards, human factors/ergonomic hazards, and environmental hazards. It describes hazard analysis in terms of failure modes and effects analysis, failure modes and criticality analysis, fault tree analysis, fault hazard analysis, and operating hazards analysis. The article discusses fail-safe designs, such as fail-passive designs, fail-active designs, and fail-operational designs, to ensure that a failure will either not affect the product or change it to a state in which no injury or damage will occur. It also provides information on the various types of warnings, such as visual warning, auditory warnings, olfactory warnings, tactile warnings, and tastable warnings.