Nitrogen hypoxia discontinued in euthanizing animals, why is it ok for humans?

NEW ORLEANS, La. (KTAL/KMSS) – A group of veterinarians and animal welfare providers in Louisiana gathered to share their opposition to the state’s decision to resume executions using nitrogen hypoxia.

Louisiana’s first execution in 15 years was set for March. However, Christopher Sepulveda died on Saturday, February 22, 2025, after 30 years on death row at the Louisiana State Prison in Angola.

The animal care providers, Veterinarians Against Gassing, gathered with signs and professional expertise to urge state lawmakers, including Governor Landry, to reconsider the state’s chosen method of execution. Members of the group expressed that they have different political ideologies and backgrounds and have differing opinions about the death penalty. However, they were all gathered to express their opposition to the method they call inhumane, which has been mostly abandoned by their industry.

Companion animal euthanizations used to employ nitrogen hypoxia; however, after years of advocacy, all but two states have discontinued the practice either voluntarily or through legislation. The method was changed because, according to the experts, it is an inhumane way to die.

“It causes an undue amount of fear, stress, and anxiety in that animal,” Veterinarian Dr. Mike Greenberg said. “The reason for this is the mechanism through which it works. With gas asphyxiation, a state of hypoxia is induced, and that just means that a lack of oxygen or inadequate amount of oxygen is being delivered to the brain, the heart, the lungs, tissues of the body and that leads to death.”

The reason this method was considered inhumane and is mostly discontinued for companion animals is because the animals are awake when the gas is administered, which leads to fear, anxiety, stress, and prolonged death.

Those who administered the method, according to Greenberg, described graphic scenes that included seizures, bleeding from the nose and mouth, and other issues as the animal died. Those in attendance of the nation’s first execution by nitrogen hypoxia shared similar disturbing details after attending the execution of Kenneth Smith in Alabama earlier this year, who was the first person to die in the U.S. by administration of gas for execution.

According to Death Penalty Info, wit­ness­es report­ed that Mr. Smith appeared awake for sev­er­al min­utes after the nitro­gen gas began. They observed that he ​“shook and writhed” for at least four min­utes before breath­ing heav­i­ly for anoth­er few min­utes. ​“This was the fifth exe­cu­tion that I’ve wit­nessed in Alabama, and I have nev­er seen such a vio­lent reac­tion to an exe­cu­tion,” said media wit­ness Lee Hedgepeth.

Nitrogen hypoxia differs from nitrogen, which is filtered out when breathing. When used in execution, the nitrogen is concentrated at a level that displaces oxygen, reduces the available oxygen to breathe, and eventually causes asphyxiation.

Governor Landry provided the following summary of Louisiana’s execution by nitrogen hypoxia:

Execution by nitrogen hypoxia is accomplished by placing a mask on the inmate’s face and
replacing oxygen with nitrogen gas. The inmate will be allowed access to a spiritual advisor. Designated victim relationship witnesses and designated media representatives will be authorized to witness the execution in accordance with the protocol and Louisiana law.
The Louisiana State Penitentiary personnel will conduct checks on all aspects of the nitrogen
system and other apparatus utilized in the protocol prior to the commencement of the execution.
Once escorted to the death chamber, medical monitors will be attached to the inmate to evaluate the relevant vital signs. The inmate will be offered the opportunity to make a final statement, and then, the specialized mask for administration of the nitrogen will be fitted onto the inmate. At the designated time, pure nitrogen gas will be administered to the inmate through the mask for a sufficient time period necessary to cause the death of the inmate. In accordance with the protocol, the coroner will then be asked to confirm the death. The Warden of Louisiana State Penitentiary will then make a statement confirming that the execution has been completed in accordance with the laws of the State of Louisiana.
Louisiana Governor Jeff Landry