ShareProbe into fatal cryotherapy accident at a gym in Paris
After a woman died in a cryosauna in Paris, the IIR provides technical insights.
A serious accident occurred on Monday, April 14, 2025 during a cryotherapy session at a sports centre located in the 11th arrondissement of Paris. An employee died and a client was hospitalised in critical condition due to a nitrogen leak in the establishment’s partial-body cryotherapy cabin.
According to initial information from Paris Public Prosecutor’s Office and emergency services, a nitrogen leak caused the poisoning of the two victims, who were found in cardiopulmonary arrest.
The employee, aged 29, was supervising the session when she lost consciousness. The client, aged 34, was transported to the nearby Lariboisière Hospital in a life-threatening condition. Three other individuals, who attempted to assist the victims, were also hospitalised, though their lives were not in danger.
The gym, which held around 150 people at the time of the incident, was fully evacuated. An investigation has been launched to determine the precise causes of the accident. It has been handed to the Paris 11th arrondissement police station, jointly with the State Labour Inspectorate. An autopsy and toxicological analyses are currently underway.
According to the arrondissement mayor, a nitrogen cylinder had been replaced that morning. The hypothesis of a malfunction in the ventilation system is being considered.
The accident has provoked strong emotions in Paris and was rapidly reported by many international media and on social media platforms. It has also rekindled questions regarding wellness practices involving industrial gases in enclosed environments.
Technical insight
The IIR, through its “Whole-Body Cryotherapy” Working Group, wishes to shed some technical light on the different types of cryotherapy equipment and reiterate safety requirements.
There are several types of cryostimulation devices:
- Cryosaunas, used for “partial-body” cryotherapy, operate by injecting liquid nitrogen directly into a chamber that remains open at the head level. This technology carries a known risk of anoxia (oxygen deficiency) if the gas is not properly evacuated. This was the type of device used in the Paris incident.
- “Whole-body” cryotherapy is conducted in sealed chambers, where cooling is achieved via an indirect system, without direct contact between the refrigerant gas and the ambient air the user breathes. These devices are designed to maintain a breathable atmosphere inside the chamber.
Nitrogen is an odourless, colourless industrial gas, and its use demands specific precautions. Historically confined to professional domains – industry, health, research – its use in wellness or sports settings requires implementing strict preventive measures. These include operator training, installation of appropriate ventilation devices and of gas and oxygen detectors, and thorough monitoring of equipment.
In France, the use of potentially hazardous substances in enclosed environments is governed by the French Labour Code, particularly concerning management of premises with specific pollution levels (articles R.4222-3 to R.4222-17) [1]. These provisions recall the obligation to ensure effective ventilation adapted to the nature of the pollutants, and regular inspection of facilities.
Additional recommendations have been put forward by the French Compressed Gas Association (AFGC) [2].
However, there is currently no dedicated label allowing users to verify compliance with these safety measures in establishments equipped with cryosaunas.
More information is available in open access in our Technical Brief on whole-body cryotherapy (available in English).
[1] Locaux à pollution spécifique (Articles R4222-10 à R4222-17) (in French)
[2] Cryothérapie : recommandations pour une utilisation en sécurité de l’azote liquide (in French)
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