The hazards of liquid nitrogen stem mainly from two of its properties: it is very cold, and a small amount of liquid nitrogen converts to a large amount of gas.
12.6.1 Hazards of Liquid Nitrogen
At temperatures between -100°C and -192°C, liquid nitrogen can cause frostbite on skin and severe burns to the eyes. The gas released from the liquid is very cold and can cause eye damage. Note that the cloudy vapor is moisture condensed by the cold, not the nitrogen gas, which is colorless, odorless and tasteless.
Liquid nitrogen exposed to the air in a poorly ventilated room could release a sufficient amount of gas to displace atmospheric oxygen and cause unconsciousness and asphyxiation.
12.6.2 Handling Procedures for Liquid Nitrogen
- Avoid all contact with liquid nitrogen and non-insulated pipes or vessels containing liquid nitrogen (very cold metal will stick fast to flesh).
- Wear protective clothing:
a. Wear insulated or leather gloves when removing anything from a liquid nitrogen freezer. Gloves should fit loosely so they can be thrown off if liquid spills or splashes into them.
b. Wear a buttoned lab coat or full apron.
c. Wear a face shield over goggles when removing and when working with anything from a liquid nitrogen freezer.
d. Wear closed shoes (as opposed to sandals).
12.6.3 Storage of Liquid Nitrogen
- Liquid nitrogen freezers and tanks must be in ventilated rooms (e.g., they are not permitted in cold rooms).
- Place sample racks or any object into liquid nitrogen slowly to minimize boiling and splashing, and to prevent explosions.
- Use only internally threaded cryogenic vials in liquid nitrogen freezers and screw the caps on tightly. An externally threaded vial can explode when removed from a liquid nitrogen tank. Liquid nitrogen can seep under the cap and become trapped between the threads. The gas expands when at room temperature and the pressure can cause the vial to explode, sending plastic shards toward the operator's face.
- Contact EH&S for additional safety information if you plan to use liquid nitrogen outside a freezer.
12.6.4 Emergency Response: Exposure
Immediately warm the areas affected by frostbite with near-body-temperature warm water. If the skin is blistered or the eyes are affected, proceed to the nearest hospital emergency room.
Complete an Accident-Illness Report Form as soon as possible and mail to EH&S at J3-200.
12.6.5 Emergency Response: Spills
Evacuate the area and allow the liquid to evaporate.