The world today has become alarmingly vulnerable to natural crises and industrial disasters and their consequences. A crisis is an event that inflicts significant human casualties and financial and environmental damage on society in a short period of time, such that addressing the effects of these events requires fundamental and extraordinary measures.

Because few people can think clearly and rationally during a crisis, it is important to be prepared to respond to such situations. Emergencies can be natural or man-made, such as floods, storms, fires, releases of toxic gases, or chemical spills.