Alabama lawmakers have approved a new method of execution, by nitrogen hypoxia.

Death would occur by forcing the inmate to breathe only nitrogen, with no life-sustaining oxygen. The method has never been used although it has been authorized by two other states.

Gov. Kay Ivey could sign the bill into law. It passed the House of Representatives tonight by a vote of 75-23. The Senate had passed the bill, by Sen. Trip Pittman, R-Montrose, in February by a vote of 29-0.

Lethal injection is Alabama's main method of execution. Condemned inmates can choose electrocution over lethal injection, although none have done so since the state adopted lethal injection.

The bill would add nitrogen hypoxia as a third option. Also, if lethal injection were ruled unconstitutional or otherwise became unavailable, nitrogen hypoxia would become the state's method.

Daniel Sparkman, Ivey's press secretary, said the governor would decide what action to take on the bill after a review by her legal team.

Mississippi and Oklahoma have also adopted nitrogen hypoxia as a form of execution, although the method has never been used.