The first-ever execution by nitrogen gas is set to go ahead in America today, January 25.

Alabama hitman, Kenneth Smith, 58, was sentenced to death for killing a woman on behalf of her preacher husband in 1988 and was due to be executed by lethal injection in November 2022 but survived after it was botched.

Alabama, one of only three states to have legalized nitrogen executions ruled that Mr Smith would be put to death via nitrogen instead.

The execution will be performed between 2 am Thursday and 6 am Friday central time, during which legal teams have the chance to log last-minute appeals.

Similar to a lethal injection, Mr Smith will be strip-searched and secured with restraints on his arms and legs before being led into the execution room by guards.

He will then be strapped to a gurney and unable to move any of his limbs. Mr Smith will then have a mask known as a ‘Type-C full facepiece supplied air respirator’ strapped to his face.

This is a type of mask that’s usually used in industrial settings to deliver oxygen. In Mr Smith’s case, he will be forced to breathe pure nitrogen. 

The warden will read the death warrant and ask Mr smith if he has any last words. He will then exit the room and activate ‘the nitrogen hypoxia system.’ 

The state claims it should take a few seconds for the gas to knock Mr. Smith unconscious and between five and 15 minutes to kill him.

Experts say the method ‘humane could cause excessive pain and humiliation, warning he could be left in a vegetative state instead of dying or could choke to death on his own vomit.

The American Veterinary Medical Association has ruled that the execution method is too cruel to be performed on most animals because the suffocation process is too ‘distressing for some species.’

Officials from the United Nations have said it could breach human rights treaties that forbid ‘torture or other cruel, inhuman or degrading treatment or punishment.’