Liquid nitrogen is a form of liquefied atmospheric gas that is used in cryogenics, the freezing of foods for transport, and in medicine and scientific research. Liquid nitrogen is transported in pressurized tanks called Dewars. Because nitrogen gas occupies 700 times as much volume as the liquid, displacing oxygen, evaporation in confined spaces can lead to asphyxiation or explosions. Before purchasing or handling liquid nitrogen, it's important to know the proper safety precautions.
Read about liquid nitrogen safety before purchasing a tank. Understand what to use and what not use around liquid nitrogen. For example, thick cryogenic gloves and safety goggles are a must to protect your hands and eyes. Set up a plan for what to do in any possible worst-case scenario, such as an accidental spill of liquid nitrogen.
Search online to determine the amount of liquid nitrogen you need in case you need to purchase more than one Dewar.
Call your local welding supply company or gas supplier store ahead of time to let them know how much liquid nitrogen you need.
Go to the store to purchase one or more 5-gallon (25-liter) Dewars of liquid nitrogen. Make sure to purchase a Dewar with a loose-fitting stopper; this prevents gas pressure buildup. Also, while at the store, purchase any other necessary equipment such as cryogenic gloves.
Prepare to give a reason for purchasing the liquid nitrogen. Depending on the store's policy of selling liquid nitrogen, you may be required to sign an agreement of purchase and use for the store's legal protection in case the use of liquid nitrogen results in personal injury or property damage.