5 Steps to Protect Liquid Nitrogen Dewar Contents
by Sarah Sameei, Intern for Control Company
For the long-term storage of sensitive biologicals, the liquid nitrogen dewar is a system that provides the optimal environment of a stable, low-temperature necessary to maintain the life of delicate cells. The dewar is a non-pressurized vessel that is specifically designed and made of materials that can withstand the extreme temperatures associated with liquid nitrogen. Liquid nitrogen is odorless, colorless, tasteless, and nonirritating; therefore, it has no warning properties and must be carefully handled. With a boiling point at a low temperature of -196˚C, liquid nitrogen is considered a cryogenic liquid and can be used to store organisms with limited life spans.
With cryopreservation being possible due to liquid nitrogen, medical procedures and research can be further advanced with biologicals like stem cells, tissues, and other samples being kept alive forever in liquid nitrogen dewars.
Here are five steps to protect your liquid nitrogen dewar and its contents:
- Use a reliable temperature monitoring system. To stop any biochemical reactions that could result in cellular degradation, most sensitive biologicals should be maintained at very low temperatures within the dewar. Lower storage temperatures such as -196˚C enable organisms with limited life spans to remain alive forever. The most effective method to guarantee the safety and consistently low temperature of the dewar’s contents is to implement a dependable liquid nitrogen temperature monitoring system.
- Always keep the dewar upright. The dewar should remain in an upright position at all times to ensure safe storage. Tipping the dewar over or laying it on its side could result in spillage of liquid nitrogen. Damage to the dewar or to any materials stored within could occur as well.
- No rough handling. Rough handling can cause major damage to dewars and contents inside. Dropping the dewar, allowing it to fall over on its side, subjecting it to sharp impact and severe vibration can result in partial or complete loss of vacuum. The vacuum insulation system reduces the conduction heat load on the cryogenic liquid and allows the dewar to maintain a cold temperature consistently. A steadily low temperature allows for the vitality of cryo-needs.
- Keep unit clean and dry. The unit should be placed in a clean and dry area. Moisture, chemicals, strong cleaning agents, and other substances could promote corrosion and should be removed immediately. Simply use water or a mild detergent to clean the dewar and dry it thoroughly to prevent corrosion of the metal shell. Damage to the materials with which the dewar is made could put stored objects at risk.
- Maintain adequate ventilation. The entrance of any liquid nitrogen dewar should never be covered or plugged to not interfere with the venting of gas. Dewars are non-pressurized and, therefore, inadequate venting can lead to excessive gas pressure. This could result in the dewar bursting open and becoming a safety hazard for personnel and stored organisms.
While there are no official guidelines regarding cryogenic storage, the overall goal is to maintain the correct low temperature within the dewar. Refilling the dewar with liquid nitrogen following the correct static holding time and utilizing a calibrated liquid nitrogen temperature monitoring system are the best ways to ensure safety of stored biologicals.