Female Employee killed, Client in Critical Condition After Nitrogen Poisoning During Cryotherapy at Paris Gym

On Air gym on the Boulevard Voltaire

A tragic cryotherapy accident at the On Air Voltaire gym in the Popincourt district of Paris has left one woman dead and another in critical condition following a suspected nitrogen leak during a session on Monday afternoon.

The 29-year-old victim, a gym employee, and a 34-year-old client both collapsed after nitrogen gas reportedly displaced oxygen inside the ultra-cold cryotherapy chamber. The chamber had undergone maintenance earlier the same day. The sudden drop in oxygen caused both women to suffer cardiorespiratory arrest just before 6:30 p.m. local time.

Emergency responders rushed to the scene, but despite attempts to resuscitate the staff member, she was pronounced dead on site. The client was transported in critical condition to Lariboisière Hospital and remains in intensive care. Three other employees suffered minor injuries and were treated at the scene. Approximately 150 people were evacuated from the facility as a precaution.

According to initial findings, a nitrogen leak from the cryo-chamber is thought to have caused the poisoning, a source close to the investigation said. An employee of the gym, who was in her late 20s, died

The management of On Air Voltaire has since closed the facility indefinitely and stated that they are cooperating fully with authorities to investigate the incident and determine the exact cause of the nitrogen leak.

French prosecutors have initiated a formal investigation, ordering both an autopsy and toxicological tests on the victims to assess the full impact of the gas exposure.

In a post promoting the practice of cryotherapy, On Air claimed that it would provide several benefits

Cryotherapy, the treatment at the center of the incident, involves exposing the body to extremely low temperatures—sometimes as cold as -140°C (-220°F)—using liquid nitrogen or similar substances. The therapy is often promoted for its potential health benefits, including reduced muscle inflammation, accelerated recovery, and improved blood circulation, and is popular among athletes like Floyd Mayweather and LeBron James.

Despite its popularity, cryotherapy remains controversial due to inconsistent scientific findings on its effectiveness and significant safety concerns. Inadequate ventilation in cryotherapy chambers can result in dangerous oxygen displacement, posing severe health risks including asphyxiation, frostbite, and burns.

Cryotherapy sees the body subjected to sub-freezing temperatures, usually through the use of nitrogen gas.

Health authorities and safety organizations, including the European Industrial Gases Association, have previously warned of the potential dangers associated with nitrogen use in cryotherapy. In 2018, the association specifically cautioned against the risk of oxygen depletion and the possibility of suffocation in poorly ventilated spaces.

Medical experts also note that the supposed benefits of cryotherapy may be achievable through simpler and safer alternatives, such as applying ice packs or engaging in cold water immersion.

This incident has renewed concerns about the regulation and safety protocols of cryotherapy services, particularly in fitness centers and spas.