In an IVF laboratory context, cryogenic dewars fall broadly into two categories based on their function, and understanding this distinction matters for both equipment planning and daily workflow.
A long-term storage dewar is the primary vessel in which patient embryos and gametes are held for extended periods, from days to years. It is designed for minimal disturbance, low evaporation, and maximum sample capacity. Ideally, the long-term storage dewar should be opened as infrequently as possible, because every opening allows cold nitrogen vapour to escape and warm room air to enter. Each opening event contributes to nitrogen evaporation and briefly disturbs the temperature environment.
A working dewar, sometimes called a procedure dewar, is a smaller vessel used during active procedures. When an embryo or gamete sample needs to be retrieved for transfer or clinical use, it is accessed from the long-term storage dewar and immediately placed in the working dewar to maintain cryogenic conditions while the procedure is prepared. Similarly, freshly vitrified samples may be temporarily held in the working dewar before transfer to their designated long-term storage position.
Using a working dewar protects the long-term storage dewar from the increased evaporation and temperature disturbance that would result from leaving it open during a clinical procedure.
The working dewar does not need to meet the same capacity or hold-time specifications as the long-term storage dewar. It is optimised for accessibility and ease of handling rather than long-term static performance.
For IVF laboratory equipment planning, visit Cryolab at cryolab.co.uk“>cryolab.co.uk
