A former safety manager has been sentenced to one year and seven months in prison in connection with the death of a five-year-old Michigan boy who was killed in a fiery January 2025 explosion inside a hyperbaric oxygen chamber.

Jeffrey Mosteller, 66, received that sentence after pleading no contest to involuntary manslaughter in Oakland county circuit court in Michigan on Monday.

He worked as the safety manager at the Oxford Center, an alternative healthcare facility that treats children with a range of health conditions – including autism, ADHD and autoimmune diseases – using hyperbaric oxygen therapy.

Mosteller faced up to 15 years in prison before being handed his 19-month sentence.

Five-year-old Thomas Cooper, of Royal Oak, Michigan, was undergoing treatment for attention deficit hyperactivity disorder (ADHD) and sleep apnea at the Oxford Center in the Detroit suburb of Troy when a fire erupted inside the hyperbaric chamber. That triggered an explosion which killed Cooper.

According to an expert who viewed video of the case, the child had squirmed enough to pull the sheet off a mattress inside the chamber, causing a spark of static electricity. That spark became a flash fire that incinerated him within seconds because of the oxygen-rich environment surrounding him.

Cooper’s mother was badly burned on her arms and chest while desperately trying to open the tank.

Mosteller is one of four former Oxford Center employees charged in connection with Thomas’s death. The other three were still awaiting trial at the time of his sentence.

The Oxford Center founder and chief executive, Tamela Peterson, 58, was charged with second-degree murder. Facility manager Gary Marken, 65, was charged with second-degree murder and involuntary manslaughter. And Aleta Moffitt, 60, who was operating the chamber when it exploded, was charged with involuntary manslaughter and intentionally placing false medical information on a medical records chart.

The US Food and Drug Administration (FDA) has cleared hyperbaric chambers to be marketed as safe and effective for 13 disorders, including severe burns, decompression sickness and non-healing wounds. The therapy works by delivering pure oxygen to a person’s body inside a pressurized chamber.

Despite its FDA approval in certain cases, hyperbaric oxygen therapy (HBOT) has been a growing source of controversy as the safety of these chambers have been called into question. Many allies of Trump administration health secretary Robert F Kennedy Jr have endorsed HBOT, but many others have expressed skepticism towards the treatment’s increasing push into the healthcare mainstream.

Cooper’s parents filed a $100m wrongful death lawsuit against the clinic and the chamber’s manufacturer over their son’s death.