The Arizona Department of Corrections has refurbished a gas chamber and plans to execute death row inmates with Zyklon B, a cyanide-based pesticide used during mass murders at Nazi concentration camps.

The Arizona gas chamber hasn’t been used in decades. Last year, according to The Guardian, Arizona officials detonated smoke grenades in the room and resorted to “astonishingly primitive” methods to ensure that the perimeter was secure:

Prison officials checked for gas seepages with a candle.

The flame of the candle was held up to the sealed windows and door and if its flame remained steady and did not flicker the chamber was deemed to be airtight. In December staff declared the vessel “operationally ready”.

Chemicals used in lethal injections have been in short supply, delaying executions across the country. Last month, the South Carolina House passed a law re-instating death by firing squad.

The Guardian reports that Arizona paid $1.5 million on a sedative that it hopes can be used in injections. The gas chamber is a grisly plan b.

The last prisoner killed by gas in Arizona was Walter LaGrand in 1999. It took him 18 minutes to die and an eyewitness reported “agonizing choking and gagging.”

“It’s without question that lethal gas, or as least the lethal gas that Arizona is trying to bring back, is the most gruesome of all these methods we’ve had in this country,” Fordham University law professor Deborah Denno told The Washington Post.

“You have to wonder what Arizona was thinking in believing that in 2021 it is acceptable to execute people in a gas chamber with cyanide gas,” Robert Dunham, executive director of the Death Penalty Information Center, told The Guardian. “Did they have anybody study the history of the Holocaust?”

One hundred and fifteen inmates await execution on Arizona’s death row. In 2014, the last executed prisoner took two hours to die. He was injected with lethal drugs fifteen times.