Kenneth Eugene Smith’s execution would be the nation’s first using nitrogen gas.

Lawyers for a spiritual adviser to an Alabama inmate scheduled to be executed with nitrogen gas next month said in a complaint filed Wednesday that restrictions on how close the adviser can get to the inmate in the death chamber are “hostile to religion.”

The Rev. Jeff Hood, who plans to enter the death chamber to minister to Kenneth Eugene Smith, said the Alabama Department of Corrections asked him to sign a form acknowledging the risks and agreeing to stay 3 feet (0.9 meters) away from Smith’s gas mask. Hood, a death penalty opponent, said that shows there is a risk to witnesses attending the execution. He said the restrictions would also interfere with his ability to minister to Smith before he is put to death.

“They’ve asked me to sign a waiver, which to me speaks to the fact that they’re already concerned that things could go wrong,” Hood said in a telephone interview.

Smith’s execution would be the nation’s first using nitrogen gas. The nitrogen is planned be administered through the gas mask placed over Smith’s nose and mouth while he is strapped to a gurney in the death chamber normally used for lethal injections.