It constantly composes almost 80 % of the air that we inspire in our lungs, but is no less toxic, and sometimes fatal on certain occasions. Nitrogen, who killed a young woman and very seriously intoxicated another this Monday in a gym from Paris, is an inert, colorless and odorless gas that goes to the liquid state when it is cooled beyond -196 ° C.
Used by cryotherapy in care and recovery processes for athletes, it is not without danger. It can also be the subject of diverted uses.
The dose makes the poison
We said, nitrogen naturally composes 78 % of the air we breathe (for 21 % oxygen). And as everyone knows, the important component of the air for us human beings remains oxygen.
Consequently, a nitrogen leak “may be enough to impoverish the oxygen zone and create a danger of anoxia that can be fatal”, informs us about its Air Liquide site, a world leader in gas, technologies and health and health services.
This is what seems to have occurred without the Parisian gym where the cryotherapy tank had just been put into service after having been repaired earlier in the day. The leak of odorless gas in this space confined to probably led to the asphyxiation of the victims. “For oxygen concentrations below the 18 %threshold, there is a risk of rapid fainting without the possibility of reaction until death,” warns Air Liquide.
What uses (and benefits) for athletes
The beneficial effect of the cold to promote sport recovery and the healing of shots and small muscle and joint lesions caused by sporting activity has been known for a long time. But the time of ice baths has apparently gave way to cryotherapy tanks.
If this technique was presented in 1979 by a Japanese researcher, first to treat rheumatism, it gradually won the very high level sports world in the early 2000s before appearing in France in the mid -2010s in spaces accessible to the general public with Cryosaunas. These devices promote muscle recovery, help reduce inflammation and reduce aches, or also stimulate blood circulation and promote toxins elimination.
Concretely, a Cryosauna works “by the evaporation of liquefied nitrogen coming from the external cryogenic reservoir. The temperature is between -120 and -150 ° C, ”explains the site of Sports medicine.
The latter continues: “A gas extraction system is installed to suck up the nitrogen vapors emitted during the operation of the device. During a session, the cabin user is dressed in mandatory protective clothing: thick cotton gloves and socks, as well as a cotton swimsuit. The user, standing, is only immersed until the shoulders, with the head above the level of cold gases, which allows him to breathe the ambient air. The duration of exposure is usually two to three minutes.
What checks and supervision?
A note published by French Association of Compressed Gas (AFGC), recalled in a 2016 note that “cryotherapy activity is not officially recognized by the French medical profession and (…) is therefore not the subject of any control by the health authorities”.
The legislation has evolved slightly, and if cryotherapy when it has medical aims cannot therefore be practiced only by medical personnel, its use for aesthetic purposes, or well-being (therefore sport) is not limited, specifies the mutual of health professionals (MACSF)after two judgments of the Court of Cassation of May 2022.
The installation of a Cryosauna is however accompanied by safety instructions: an oxygen detector, an emergency stop system, a ventilation and extraction system of nitrogen to the outside in a safe area, develops a 2019 document from the AFGC.
Diverted uses
Thus, two Marseille researchers of the CNRS had used its dilation properties during its passage from the liquid gaseous state to create two small “explosions”, without damage, targeting the Russian Consulate of Marseille on the day of the 3rd anniversary of the war in Ukraine.
Also, when conditioned with an oxygen atom, nitrogen, becoming therefore nitrogen oxide is used in catering, in particular to raise the whipped cream and other foams. In this form, its use is diverted for recreational purposes, as a hilarious gas and hovering by inhalation. A hilarity and a state close to the loss of knowledge due to the temporary under-oxygenation of the brain which is not without being able to leave consequences and an addiction.
