<P> During the April 6, 1992, execution of Donald Harding in Arizona, it took 11 minutes for death to occur . The prison warden stated that he would quit if required to conduct another gas chamber execution . Following Harding's execution, Arizona voted that all persons condemned after November 1992 would be executed by lethal injection . </P> <P> Following the execution of Robert Alton Harris, a federal court declared that "execution by lethal gas under the California protocol is unconstitutionally cruel and unusual ." By the late 20th century, most states had switched to methods considered to be more humane, such as lethal injection . California's gas chamber at San Quentin State Prison was converted to an execution chamber for lethal injection . </P> <P> As of 2010, the last person to be executed in the gas chamber was German national Walter LaGrand, sentenced to death before 1992, who was executed in Arizona on March 3, 1999 . The U.S. Court of Appeals for the Ninth Circuit had ruled that he could not be executed by gas chamber, but the decision was overturned by the United States Supreme Court . The gas chamber was formerly used in Colorado, Nevada, New Mexico, North Carolina and Oregon . Six states, Arizona, California, Maryland, Mississippi, Missouri and Wyoming, authorize lethal gas if lethal injection cannot be administered, the condemned committed their crime before a certain date, or the condemned chooses to die in the gas chamber . In October 2010, Governor of New York David Paterson signed a bill rendering gas chambers illegal for use by humane societies and other animal shelters . </P> <P> As implemented in the United States, the gas chamber is considered to be the most dangerous, most complicated, and most expensive method of administering the death penalty . The condemned person is strapped into a chair within an airtight chamber, which is then sealed . The executioner activates a mechanism which drops potassium cyanide (or sodium cyanide) pellets into a bath of sulfuric acid beneath the chair; the ensuing chemical reaction generates lethal hydrogen cyanide gas . Because hydrogen cyanide gas condenses at approximately 78 ° F (26 ° C), the temperature in the chamber (when it is in use) is maintained at at least 80 ° F (27 ° C). </P>

When was the last time the gas chamber was used
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