Gas chamber is a legal means of execution in some states of the United States. The condemned person is strapped in a chair in an airtight chamber. Glass globes containing cyanide drop from beneath the chair and break in a crock containing sulfuric acid. The two chemicals mix and form deadly hydrocyanic acid gas. The person loses consciousness in seconds and usually dies within five minutes. For a list of states that use the gas chamber, see Capital punishment (table) .
Seeking an alternative to the electric chair, Nevada became the first state to use the gas chamber in 1924. The last gas chamber execution in the United States occurred in 1999, but it is still legal in some states. During World War II (1939-1945), Nazi Germany used cyanide gas to murder Jews and other minorities in concentration camps. These killings came to be known as genocide and are classified as war crimes.
