Alabama's proposed procedures to carry out executions with nitrogen gas include fitting a mask over the inmate's face and replacing their breathing air with nitrogen until their heart stops.
The state described the procedures for the proposed new execution method in a redacted court filing.
Alabama is seeking to become the first state to execute a prisoner using nitrogen.
Nitrogen hypoxia has been authorized as an execution method in Alabama, Oklahoma and Mississippi, but no state has used the method to carry out a death sentence.
If Alabama carries out an execution by nitrogen, it will be the first new execution method since lethal injection was introduced in the 1970s.