Has used nitrogen hypoxia
2 statesActually carried out at least one nitrogen execution.
Alabama
The only state to actually use nitrogen at scale — and the only state permanently enjoined from using it again.
Louisiana
The only other state to actually carry out a nitrogen execution — and the state most likely to try again.
Legally authorized — never used
3 statesStatute allows nitrogen hypoxia. No execution carried out under it.
Oklahoma
The state that invented nitrogen hypoxia as an execution method — and has never used it.
Mississippi
Statutorily authorized, no protocol, no attempt.
Arkansas
Legally cleared to carry out nitrogen executions — and, alongside Louisiana, the state most likely to try next.
Under active consideration
6 statesBills introduced, executive study, or protocol litigation pending.
Ohio
Legislation repeatedly introduced; no floor vote.
Nebraska
Executive study underway.
Arizona
Protocol litigation pending.
Tennessee
Interim study committee — no bill.
Texas
Bills introduced repeatedly; none advanced.
Florida
Legislative interest, no protocol.
State entries drawn from Suffocation by Design (2nd ed., 2026) and each state's execution statute and corrections filings.