A chemical emergency occurs when a hazardous chemical has been released and the release has the potential to harm people's health. Chemical releases can be unintentional, as in the case of an industrial accident, or intentional, as in the case of a terrorist attack. Chemical warfare agents are poisonous vapors, aerosols, liquids or solids that have toxic effects on people, animals or plants. They can be released by bombs sprayed from aircraft, boats or vehicles, or used as a liquid to create a hazard to people and the environment. Some checmical agents may be odorless and tasteless. They can have an immediate effect or a delayed effect. While potentially lethal, chemical gases are difficult to deliver in lethal concentration. Outdoors, the agents often dissipate rapidly. Chemical agents are also difficult to produce.
Some hazardous chemicals have been developed by military organizations for use in warfare. Others are found in nature. Some could be made from everyday items such as household cleaners. These types of hazardous checmicals also could be obtained and used to harm people, or they could be accidentally released.
National Disaster Education Coalition: American Red Cross