Alabama has moved one step closer to allowing death row inmates to be executed with nitrogen gas, which it claims was a "more humane" method than lethal injection or electrocution.

The new method involves the inmate being sealed in an airtight chamber which is pumped full of nitrogen gas, causing death due to lack of oxygen, known as hypoxia. Nitrogen hypoxia is currently not used as an execution method anywhere in the world.

Alabama's Senate Judiciary Committee approved the nitrogen hypoxia bill by a majority of 11 to 1 on Wednesday (14 February).

Senator Trip Pittman, who sponsored the bill, argued that nitrogen hypoxia offers a "more humane" alternative to lethal injection or the electric chair.

He said he supported the death penalty for inmates who had committed heinous crimes and argued that using nitrogen gas could be a painless way to put an inmate to death.

Pittman said that Alabama needed another execution method as lethal injection faces numerous legal challenges.

In recent months, several death row inmates have launched lawsuits against US states where they have been sentenced to death. Most have not been successful in overturning the judgement but have precipitated significant delays.

Oklahoma and Mississippi have already passed laws allowing execution by nitrogen hypoxia. So far no executions via this method have taken place, according to the Associated Press.

Robert Dunham, executive director of the Death Penalty Information Center, said the states used nitrogen hypoxia as a backup method in case complications arose with the lethal injection.

Senator Linda Coleman-Madison said she opposed the death penalty, but that she had nevertheless voted in favour of the bill as she believes nitrogen hypoxia to be a more humane method. Senator Bobby Singleton was the only one to vote against the bill.

Following the committee's approval, the bill has moved to the Senate floor.