The 50 litre dewar has been in IVF labs for decades. Here is why it is still there.
Some pieces of lab equipment come and go. The 50 litre liquid nitrogen dewar is not one of them. It has been a fixture in IVF labs, andrology units, and veterinary reproduction facilities for long enough that most practitioners do not question its presence, they just order another one when the old one starts underperforming. That longevity is not accidental. The 50 litre configuration solves a genuine problem in a way that neither smaller nor much larger vessels do quite as well. The problem it solves Clinical cryogenic storage needs to be accessible, safe, and manageable without specialist infrastructure. A 20 litre dewar gets accessed constantly and refilled frequently. A 200 litre vessel requires more planning, more space, and more liquid nitrogen budget than a mid-sized clinic can justify. The 50 litre vessel sits in a range where the refill interval is measured in weeks rather than days, the vessel can be moved by two members of staff, and the sample capacity covers a meanin...