Hunter said the state plans to abandon its current lethal injection procedure, which relies on a three-drug cocktail - Midazolam, vecuronium bromide and potassium chloride - inserted into an IV.
No state or country has ever used nitrogen for executions.
Oklahoma is turning to nitrogen after it, and other states, have been unable to acquire drugs required for lethal injections due to opposition from manufacturers to their products being used for capital punishment.
Oklahoma Attorney General Mike Hunter and Department of Corrections Director Joe Allbaugh held a news conference on Wednesday announcing a change to the state's death penalty process.More news: Thames Capital Management LLC Buys New Position in Caesars Entertainment Corp (CZR)
Allbaugh told reporters that "I'm not anxious about anything" when asked about being the first state in the nation to use nitrogen for executions, BuzzFeed News reports.
Oklahoma officials announced a plan to use nitrogen gas to execute inmates once the state resumes using the death penalty, marking the first time a USA state would use the gas to carry out capital punishment.
Grand jurors said nitrogen gas would be easy and cheap to obtain for executions, simple to administer and, according to scientific research, quick and seemingly painless.
In 2014, Oklahoma drew intense scrutiny for its death-penalty procedures after the execution of Clayton Lockett gained worldwide attention.More news: Lavrov warns of 'grave consequences' of USA new strike against Syria
Oklahoma's last executions drew scrutiny in the state and nationwide.
In 2014, the execution of Clayton Lockett gained global attention when he kicked, writhed and grimaced for 20 minutes before his execution was called off; he died of a heart attack not long after.
The grand jury said it found that secrecy surrounding how the DOC obtained the drugs used in Warner's execution and allocated for Glossip's was a factor in both having occurred contrary to the lethal injection protocol. A bill that would make the electric chair the state's default execution method is now before the House Committee on the Judiciary. When nitrogen gas was approved as a backup method in Oklahoma, the corrections department said there was no protocol in place, and that remained the case Wednesday, almost two years later.
State lawmakers then passed a law approving use of the gas.More news: Found Shot To Death Inside Brooklyn Apartment
Oklahoma officials said they didn't know when executions would resume but hope to draft the new gas protocols within the next 120 days.