This chapter introduces several major warning-related concepts. Topics include the purposes of warnings and their place in the hazard control hierarchy. The who, what, when and where of warnings are described, followed by a discussion of the concepts of hazard control hierarchy and warning systems. A table of generalized design guidelines derived from the warning literature is presented. Lastly, testing using participants from the target population is recommended to verify warning effectiveness.

Over the last 2 to 3 decades, there has been extensive development of regulations, standards, and guidelines on how and when to warn. During the same time period, there has been substantial research activity on the issues of warning effectiveness. This first chapter introduces several major concepts and sets the scene for the rest of this Handbook.