Why are executions not done with carbon monoxide? It is painless
Executive summary
Carbon monoxide (CO) has been used historically in executions and mass murder—Germany used bottled CO in extermination centers in 1940 and Nazi gas vans employed CO—so the gas carries heavy ethical and practical baggage [1] [2]. Advocates such as an aide to Jack Kevorkian have argued CO can produce a quick, “extremely painless” death in assisted suicide settings [3]; but reporting and expert commentary about other hypoxic gas methods show risks to witnesses and personnel, legal pushback, and animal-euthanasia guidance that describes anoxic methods as distressing [4] [5].
1. Historical stigma: a method tied to atrocities
Carbon monoxide’s use in state and mass killings is well documented. German killing centers used bottled pure CO in 1940 and Nazi gas vans diverted engine exhaust (a CO source) to murder large numbers; several extermination camp sites later used similar means [1] [2]. That history has left CO strongly associated with industrialized mass murder in legal and cultural debates [1] [2].
2. Claims of “painlessness” — firsthand advocacy vs. broader evidence
Some practitioners in assisted suicide contexts describe CO as rapid and painless. Neal Nicol, who assisted Jack Kevorkian, told NBC News that CO produced “an extremely painless passing” with “no twitches” and death “within minutes” after dozens of cases [3]. Independent pieces repeating similar claims say gradual oxygen deprivation can be “essentially painless” [6]. Available sources do not contain peer-reviewed clinical trials proving CO is uniformly painless in executions.
3. Operational and safety concerns for prisons and witnesses
Practical risks have long complicated gas methods. Gas chambers historically used different agents (hydrogen cyanide, CO) and required strict facility controls—temperature, ventilation and explosion-proof fittings for some gases—to avoid accidental exposures [1] [7]. Modern reporting on hypoxic methods (like nitrogen) stresses the risk of gas leakage or imperfect masks that can expose staff or witnesses, and notes that an execution can be technically legal but still judged cruel if it produces suffering [4] [5].
4. Comparisons with other hypoxic methods being debated now
Contemporary debates have focused on nitrogen hypoxia because states face shortages of lethal-injection drugs. Media reporting and medical commentators caution that forced inhalation of inert gas can be distressing and pose risk to others in the room; veterinary guidance also warns that anoxic environments are not acceptable euthanasia for most mammals because they are distressing [4] [5]. Those parallels suggest legislators and courts treat hypoxia methods—including CO—with skepticism [4] [5].
5. Legal and ethical friction: cruelty, public perception, and liability
U.S. law requires execution methods not to be “cruel and unusual”; courts and human-rights bodies scrutinize anything causing substantial distress or unpredictability [4]. The Nazi-era associations and the risk of visible suffering or procedural failures amplify public and legal resistance to gas methods, including CO [1] [2]. Available sources do not cite a modern U.S. jurisdiction adopting CO as the primary execution method.
6. Supply and control vs. historical alternatives
Part of the modern shift away from older methods lies in a mixture of supply, procedure, and optics. Lethal injection became dominant since the 1980s, but drug shortages and botched injections have prompted exploration of alternatives like nitrogen; carbon monoxide has been proposed by advocates but not taken up widely, likely because of safety, legal, and reputational obstacles [5] [3]. Available sources do not provide evidence that states are seriously poised to replace current methods with CO en masse.
7. The evidence gap and how reporting frames it
Advocates’ anecdotes (Kevorkian’s aide) and journalistic shorthand (“essentially painless”) appear in the record [3] [6]. But the peer-reviewed, clinical or forensic literature demonstrating reliably painless, controllable, and safe CO executions, especially in modern prison settings, is not present in the supplied sources—creating an evidence gap that policymakers and courts must confront. Where sources exist, they emphasize history, practical hazards, and the contested nature of “humane” execution [1] [4] [5].
Limitations: This article relies only on the supplied reporting. It highlights documented historical use, advocacy claims, and modern debates about hypoxic methods; it does not make medical or legal determinations beyond what those sources state [1] [3] [4] [5].