Do not ever cover or plug the entrance opening of any liquid nitrogen Dewar’s. Do not use any stopper or other device that would interfere with venting of gas.
These cryogenic liquid containers are generally designed to operate with little or no internal pressure. Inadequate venting can result in excessive gas pressure which could damage or burst the container. Use only the loose-fitting neck tube core supplied or one of the approved accessories for closing the neck tube. Check the unit periodically to be sure that venting is