Condemned Alabama inmates could choose a new method of execution -- by nitrogen hypoxia -- under a bill that passed the Alabama Senate today.

Sen. Trip Pittman, R-Montrose, said the method would be more humane than lethal injection and would be a ready alternative if lethal injection is ruled unconstitutional or the state becomes unable to obtain the drugs.

Oklahoma and Mississippi have passed similar laws allowing execution by nitrogen hypoxia, the Associated Press reported. But no state has used it to carry out an execution, according to the Death Penalty Information Center.

Nitrogen is a naturally occurring gas in the air we breathe. A person allowed to breathe only nitrogen would die from deprivation of oxygen.

The bill moves to the House of Representatives. It passed the Senate by a vote of 29-0.

Alabama carries out death sentences by lethal injection at Holman Prison in Atmore. Inmates can choose death by electrocution, though none have done so since the state adopted lethal injection in 2002.

Pittman's bill adds nitrogen hypoxia as a third option.

Alabama is scheduled to execute Doyle Lee Hamm tonight for capital murder of a Cullman motel clerk during a robbery in 1987.