A dry shipper is a vacuum insulated cryogenic container that holds liquid nitrogen absorbed into a porous liner rather than as free liquid. That single design decision is what makes it shippable. There is no liquid to spill, no pressure to build, and nothing to leak if the vessel is knocked over in transit.

It is also what separates a dry shipper from every other vessel in the laboratory, and what determines how long it will actually keep your samples cold.

How a dry shipper works

Before use the shipper is charged with liquid nitrogen until the absorbent liner is fully saturated, usually over several hours. The remaining free liquid is then poured off. What stays behind in the liner is enough to hold the interior at cryogenic temperature for the length of the journey.

Samples travel inside in sealed straws, vials or cryovials held in canisters. Because there is no liquid phase, samples never sit in shared liquid nitrogen during transport.

Why it can be shipped when a dewar cannot

This is the part most guides get wrong. A dry shipper is not “IATA approved”. It is not restricted, which is a different and more useful thing.

Special Provision A152 of the IATA Dangerous Goods Regulations covers insulated packagings containing refrigerated liquid nitrogen fully absorbed in a porous material. Provided the design cannot build pressure and cannot release liquid nitrogen in any orientation, such packagings are not subject to the regulations when carrying non dangerous goods. Harvard University’s environmental health and safety guidance sets out the same position and the declaration wording used in practice.

Free liquid nitrogen shipped as a refrigerated liquid is a different matter entirely. That is UN 1977, Class 2.2, and it falls under the full dangerous goods rules for both air and road. The distinction rests entirely on whether liquid is present and whether pressure can build.

How long a dry shipper actually holds temperature

Manufacturer hold times are measured on a fully charged vessel, standing upright, unopened, at moderate ambient temperature. Your journey is unlikely to match that, and three things shorten it:

• Charge quality. A shipper filled, allowed to saturate properly and then drained will outlast one charged in a rush before the courier arrives.
• Orientation. Laid on its side in a van, a shipper loses hold time it was never rated to lose.
• Ambient temperature. A hot vehicle in summer is not a laboratory corridor.

ESHRE’s 2026 good practice recommendations for the IVF laboratory set the standard plainly: dry shippers should be validated for maintenance below minus 150°C for the maximum anticipated transport duration. That means logging your own shipper, charged your own way, under conditions resembling the real journey. A cryogenic data logger with a PT1000 probe produces the temperature trace that evidences it.

The CryoStork range and how to size one

Cryolab’s CryoStork® dry shippers come in five sizes:

• CryoStork® V2, 2 litres, 398 mm high by 180 mm wide
• CryoStork® V3, 3 litres, 441 mm by 224 mm
• CryoStork® V4, 4 litres, 505 mm by 224 mm
• CryoStork® V6, 6 litres, 435 mm by 300 mm
• CryoStork® V10, 10 litres, 584 mm by 300 mm

Size against your longest realistic journey rather than your average one, because the cost of a shipper that runs out of hold time is the shipment. Foam lined protective cases are available for the V3, V4, V6 and V10 for journeys that involve couriers rather than a member of staff.

Dry shipper, storage vessel or dewar

Three different jobs, three different vessels, and they are not interchangeable.

• Dry shipper. No free liquid. Built to travel. Hold time measured in days.
• Storage vessel. Holds liquid nitrogen, stays in one place, optimised for low evaporation and organised rack access over years. See the CryoNest® range.
• Dispensing dewar. Holds working liquid nitrogen for decanting at the bench, with a wide neck and a pump.

Common questions

Can a dry shipper be recharged? Yes. Once it has returned to room temperature it is charged again with liquid nitrogen following the manufacturer’s procedure, saturated, and drained of free liquid before dispatch.

What temperature does it hold? Below minus 150°C is the threshold professional guidance validates against. The exact profile depends on the model, the charge and the journey, which is why the trace matters more than the brochure figure.

What records should travel with it? Shipper serial number, charge date and time, confirmation that free liquid was removed, and the temperature log, alongside the sample identifiers and consent documentation.

To match a shipper size to the journeys your laboratory actually makes, or to talk through validation records before an inspection, the Cryolab team can help.