How to Store Liquid Nitrogen
Liquid nitrogen is a cryogenic substance, and according to the MIT Chemistry website, cryogenic substances can greatly affect metal and other materials due to their corrosive qualities and extreme temperatures. Containers used to store liquid nitrogen must be made of material that is strong enough for prolonged exposure to the liquid; otherwise, its extreme temperature and the pressure of the liquid can lead to an implosion. To reduce risk, glass Dewar flasks are often used to store liquid nitrogen; these flasks must always be taped or stored in metal containers.
Oxygen
The MIT Chemistry website states that a liquid nitrogen trap must be handled with extreme care and should not be opened until the trap has been removed from the coolant. These measures should be taken because the trap will be exposed to oxygen when it's opened. When oxygen combines with liquid nitrogen, the mixture can become unstable and lead to the likelihood of an explosion. Leaving the trap to warm to room temperature before opening it will stabilize the trap and minimize risk.
Cryogenic Burns
Safety goggles and protective gloves should be worn at all times when handling liquid nitrogen traps, according to the MIT Chemistry website. In addition, the website for the physical and theoretical chemistry laboratory at Oxford University points out that liquid nitrogen can cause severe burns when it comes into contact with the skin or splashes into the eyes. If liquid nitrogen comes into contact with clothes, it can stick the clothes to the skin and cause a serious burn. Liquid nitrogen can also splash onto the skin and stick to jewelry, leading to a prolonged burn, and handling a container with liquid nitrogen in it can lead to the container becoming stuck to the skin. A cryogenic burn can have serious effects, including permanent tissue damage and scarring.
Asphyxiation
When handling a liquid nitrogen trap, it's important to ensure that the liquid inside it isn't allowed to evaporate. The MIT Chemistry website explains that if liquid nitrogen evaporates, the oxygen levels in the air become reduced. This oxygen reduced air settles at ground level, and breathing in this air can cause a person to become dizzy and to become unconscious. Prolonged exposure to the oxygen-depleted air can cause the airways to become blocked, leading to asphyxiation. Keeping the working area well ventilated should help to reduce this risk.