Liquid nitrogen
Nitrogen (or dinitrogen, according to chemists, the chemical symbol of which is N2) is ubiquitous on earth. It is present in the air that we breathe, and as a result is not toxic.
Liquid nitrogen is made from compressed, purified air. Then, the extracted gasses are liquified (oxygen and nitrogen for the most part). Liquid nitrogen and nitrogen gas are colourless, odourless and flavourless. At normal atmospheric pressure, liquid nitrogen turns into steam at − 196°C.
Liquid nitrogen is being used increasingly in a wide variety of fields: 
food (fast freezing) industry (cooling of processed and ventilated air, high conductivity, cutting, grinding, cleaning) IT (overclocking) education and research (physics, preservation of plant cells) veterinary science (preservation of animal cells) medicine (cryosurgery, cryotherapy, preservation of cells and human tissues).
The hazards of liquid nitrogen are: the extremely low temperature (− 196°C), the release of nitrogen gas into the confined atmosphere.
Direct contact with liquid nitrogen incurs risks of burning and frostbite. The severity of burns depends on how long contact lasts: at temperatures lower than -55°C, the skin may freeze in under 2 minutes. Repeated exposure may lead in the long term to feelings of numbness and tingling of the body areas in contact (usually hands and feet).
The rapid transformation of a litre of liquid nitrogen into 680 litres of nitrogen gas (approximately) runs the risk of asphyxia in areas that are inadequately ventilated, as it chases away oxygen in the air. Since vapours released are heavier than air, the oxygen level is generally lower at ground level.
Furthermore, breathing extremely cold air for a prolonged period can damage lungs and upper airways.
Liquid nitrogen is nonflammable. However, there is a risk of explosion if the cryogenic liquid is heated (sudden release of gas) or if its vapours are stored in an airtight container (pressure on the sides may reach 1400 bar).
Liquid gas storage and use in workplaces are governed by the sub-section “Ventilation, purification” of the French Labour Code (Art. R 232-5 and following). The provisions on workplaces subject to specific pollution stipulate that new air flows must be determined depending on the type of pollutant, and exceed 45m3/h.
There are many recommendations on the use of liquid nitrogen, but they make no mention of necessary air renewal levels in workplaces containing liquid nitrogen. 
Within the framework of drafting a decree on good practices in reproductive biology laboratories, the French Biomedicine Agency (Agence de la Biomédecine) has to integrate recommendations for preventing risks associated with the use of liquid nitrogen. The French Biomedicine Agency sent a solicited request to Afsset in a letter dated 11 April 2006 to assess the risks associated with the use of liquid nitrogen in Assistance Médicale à la Procréation (Medical Assistance with Procreation/AMP) laboratories with a view to formulating recommendation guidelines for preventing these risks.
Analysis of the request identified three main tasks: Assess risks associated with the use of liquid nitrogen in reproductive biology activities; Review the regulations applicable to cryogenic facilities; Recommend prevention guidelines for cryogenic facilities.
The scope of the French Biomedicine Agency’s solicited request will also include drawing up a list of the liquid nitrogen uses in France.
Working method:
The implementation of a collegial expert assessment was validated in October 2006 by the Afsset Committees of Specialised Experts (CSEs) “Assessment of risks associated with air environments” and “Assessment of risks associated with chemical substances”.
Chemists, doctors, reproductive biologists and engineers, who will join the working group attached to the CSE “Assessment of risks associated with air environments”, will carry out the following: validation of scientific data on nitrogen; assessment of the health effects of dinitrogen-loaded atmospheres and skin exposure, on the basis of exposure scenarios in AMP activities; recommendation of guidelines for preventing the identified risks.
Prevention guidelines will be based on: the risk assessment, the survey conducted among AMP professionals, the prevention measure study, the report of national and international regulations.
This work will take place in the first half of 2007.
The working group will be formed in December 2006, once the current call for applicants is complete.
The “Study of national and international health provisions applicable to nitrogen” is the subject of a public procurement contract under preparation. It will focus on international and national regulations in 15 European countries and North America, regarding: cryogenic facilities in general; the storage, use and land transport of liquid nitrogen, applicable to containers of less than 5000 litres; the safety of AMP laboratories.
The study of prevention measures will involve: an analysis of existing group and personal types of protection necessary in laboratory activities using liquid nitrogen; recommendations on the specifications of group protection equipment (ventilation system) and personal protection gear.
Nanotechnologies cover a large number of technological fields all of which concern nanometrically sized structures (a nanometre = 10-9 m). Electronics and information and communication technologies are examples of such fields.
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