However, if sufficient liquid nitrogen is vaporized so as to reduce the oxygen percentage to below 19.5%, you are at risk of oxygen deprivation. Asphyxiation - nitrogen is not poisonous the air is already about 78% nitrogen (oxygen makes up about 21%, and trace gases the remaining 1%).The plastic mesh with which some small thermoses are sold protects the Dewar itself to some extent, but does not protect very well against injury from glass shards resulting from implosion. Glass Dewars must be taped solidly around the outside.Remove metal jewelry/watches on hand and wrists.Guard against pressure build-up by using a pressure relief vessel or a venting lid.In the morning the coldfinger will contain LIQUID OXYGEN up to the level of the nitrogen in the Dewar. This is most alarmingly demonstrated if a person leaves his/her vacuum pump's coldfinger in a Dewar of liquid nitrogen overnight. Liquid nitrogen will condense oxygen from the air. (Cold rooms have no air changes and a person entering a room with elevated nitrogen in the air can quickly pass out and then die within several minutes of entering. Do not store container(s) of LN2 in a cold room or any other location where a person could physically enter an anoxic atmosphere.
Persons using a tipper to dispense LN2 must wear a full face shield over goggles, cryo-gloves, full length cuffless trousers which completely cover the tops of the shoes (or a full length apron), and shoes which will not permit liqufied gas to enter them in case of a spill, and which are also quickly removable in case they do (allow liquid to enter). When handling large quantities, a full length apron will minimize the chance of a spill going into your shoes, where it might destroy some cubic centimeters of flesh before you can get your shoes and socks off. Liquid nitrogen can cause terrible "burns." (Death of living tissue caused by the extreme cold.) Hand protection and goggles (not safety glasses) are to be worn when dispensing and handling liquid nitrogen.It's scary and unpleasant and could easily be quite disastrous.) 160 L of LN2 for whatever reason falls onto its side? (It happens.The funnel (which you should not be using) freezes and spews nitrogen upward into your face?.You freeze your watchband or wedding band to your finger?.A pressurized Dewar spontaneously vents?.At all times, HAVE A PLAN of what you will do if.General precautions for all use of LN2 (liquid nitrogen).Alternatively, a cryoporter or dry shipper can be used, and these are also suitable when samples need to be mailed.Calculate how much LN2 is necessary to displace all your air. For transport between different locations, dewars must be firmly secured in an open truck, utility, or trailer.Where possible, access to intervening floors should be locked out or the lift must be clearly sign-posted whilst LN2 dewars are in transit with a trained member of staff receiving the dewar at the final destination. In areas where dewars need to be transported between floors via lift, a clear procedure must be in place and available to all staff. Dewars must never be accompanied in lifts due to the risk of asphyxiation.Appropriate trolleys must be used for transporting dewars between buildings to ensure that the dewar is secure at all times.using LN2 pumps and ensuring there is adequate ventilation. Controls to minimise the likelihood of splashes, as well as exposure to escaping liquid/gases, must be in place, e.g. Only appropriately trained personnel should perform LN2 filling and transferring tasks.Domestic thermo flasks are not appropriate for this purpose, as they are not designed to be free-venting and can result in pressure build-up and a subsequent explosion. Containers that meet the requirements of AS 1894 must be used when handling small volumes of LN2 for use in the laboratory, e.g.