A cryo tank – short for cryogenic tank – is a vacuum-insulated container used to store or transport biological samples at cryogenic temperatures using liquid nitrogen. In IVF, cryo tanks are used to store sperm, embryos, and oocytes at -195.8 degrees C, the boiling point of liquid nitrogen at atmospheric pressure. The term “cryo tank” is used interchangeably with “liquid nitrogen dewar” or “cryogenic storage vessel” in most clinical and commercial contexts, though technically a dewar refers to the vacuum flask principle and a tank may refer to larger bulk storage.

What types of cryo tank are used in IVF?

Two main types of cryo tank are used in IVF: static storage vessels, which remain in the laboratory and hold samples in liquid or vapour phase nitrogen; and dry shipping vessels (dry shippers), which are charged with liquid nitrogen and transport samples in the vapour phase without free liquid. Static storage cryo tanks are specified by their canister capacity, static evaporation rate, and liquid nitrogen hold time. Dry shipper cryo tanks are specified by their hold time and IATA compliance for air transport.

How do you maintain a cryo tank in an IVF laboratory?

A cryo tank in clinical use must have its liquid nitrogen level checked and documented on a defined schedule. Most laboratories check storage vessel levels daily. The static evaporation rate of the vessel determines how frequently top-up is required. Any significant deviation from the expected evaporation rate is an early indicator of insulation failure and must be investigated.

How long does a cryo tank last?

A properly maintained cryo tank has a service life of 10 to 20 years depending on usage intensity and handling. The vacuum integrity of the outer casing determines insulation performance over time. Vessels showing increased evaporation rates, visible external frost on the casing, or mechanical damage to the neck should be assessed for replacement.

A cryo tank does not fail suddenly in most cases – it fails gradually. The warning sign is a rising evaporation rate, and the laboratories that catch it early are the ones checking their liquid nitrogen levels every day rather than every week.

Cryolab’s CryoNest and CryoCan cryo tank ranges are available at cryolab.co.uk/product-category/storage-vessels/.