Handling Liquid Nitrogen
Handling Liquid Nitrogen
This guide is provided for the use of liquid nitrogen; anyone using any other cryogenic gases should observe the appropriate additional specific precautions. For further information read the University's Health and Safety notes on Liquid Nitrogen.
General Safety Precautions
Liquid nitrogen at -196 degrees C is kept in double-walled steel vessels specifically designed for the storage and transport of cryogenic gases.
When dispensing quantities necessary for handling cryo-preserved materials, or for cooling purposes, or when transferring liquid nitrogen from one container to another, observe the following rules.
1. Work in a well-ventilated area. Nitrogen gas, continuously evolved during handling, may build up causing dizziness and, potentially, asphyxiation by displacing the air in the room.
2. Wear protective goggles, or a face-shield, thermal gloves, and a laboratory coat. Absorbent material close to the skin (e.g. gloves) should not be exposed to contact with liquid nitrogen.
3. Decant liquid nitrogen slowly, especially into vessels at room temperature, since rapid vaporisation sprays cold droplets into the atmosphere until equilibration of temperature is reached. The extremely cold vapour released during such procedures is particularly damaging to the eyes and the immersion of tubing should be avoided, as the spray issuing from the open end may constitute a hazard to those nearby.
4. Containers, other than large storage dewars, should be of rigid polystyrene (‘Styrofoam’) or double-skinned metal construction. Do not use glass or plastic ‘thermos’ flasks not designed for cryogenic gases, as there is an implosion risk from thermal shock during filling.
5. Do not touch any non-insulated surface cooled to liquid nitrogen temperatures, as adhesion of the skin will occur , due to freezing of the moisture layer at the interface, resulting in contact burns. Handle all cooled objects with tongs or forceps, and do this without undue delay, as these will also cool rapidly by conduction.
6. ALWAYS replace stoppers or lids, loose-fitting only - never seal vessels containing liquid nitrogen. Ensure vented stoppers do not ice up as this could cause excessive build up of pressure inside the vessel and thus create a risk of an explosion.
First Aid Treatment for Cold Skin Burns
1. Thaw slowly in lukewarm water
2. Cover thawed area with a sterile dressing
3. Seek medical assistance if (a) the area affected is extensive (b) the area affected is deeply frozen
4. Do not remove adhering clothing until it is thoroughly thawed