A chemical weapon is a toxic substance used to cause injury or death. It can be a solid, a liquid or a gas. Military organizations have developed many of these chemicals, such as mustard gas. Others types are used in industry or can be found in nature. Some hazardous chemicals can be made from everyday products, like household cleaners. All of these could be used in a chemical attack.

Chemical weapons can cause a wide range of symptoms, including blood poisoning, nausea and vomiting, burning eyes and lungs, choking and unconsciousness. Some can cause death.