It is a double-walled vessel with a vacuum drawn between the inner and outer walls, which minimises heat transfer by conduction and convection and keeps the contents at cryogenic temperature for extended periods with minimal boil-off of liquid nitrogen. This design is standard across almost all cryogenic storage and transport equipment used in IVF and research settings, though the quality of the vacuum and the materials used affect how long a tank holds its temperature between top-ups. Over time, a vacuum can degrade through age, damage or manufacturing defects, which is why periodic vacuum integrity checks matter as much as visual inspection. Cryolab’s storage vessels are built to hold vacuum reliably across their working life, backed by ISO 9001:2015 quality management certification.