A frozen sample shipment fails at handovers, not in transit. The vessel is usually adequate. What goes wrong is the gap between the laboratory that packed it, the courier that moved it, the customs officer who held it and the laboratory that opened it, and each of those gaps is closed with paperwork and a phone call rather than with equipment.

This is the shipping side of the decision. Whether to own or hire the vessel is a separate question, covered in Dry Shipper Hire or Purchase.

Choosing the shipper: capacity, journey, and the weight nobody accounts for

A vapour phase dry shipper holds liquid nitrogen absorbed into a porous inner matrix rather than as free liquid. Samples travel in the vapour phase, the vessel can be inverted without spilling, and there is no free liquid available to escape.

Size it on three things together: the number and format of the samples, the length of the journey including a realistic delay allowance, and who is going to lift it. The CryoStork range runs from the V2 at 2 litres through the V3, V4 and V6 to the V10 at 10 litres, and the largest unit the budget allows is usually the wrong answer: a bigger shipper is heavier for staff to handle and more expensive to ship.

Sample format matters as much as sample count. Straws, high security straws and vials occupy the canister differently, and a shipper quoted at a vial count assumes a format that is rarely yours. Ask for the calculation against the format you actually run.

Charging is where shipments are lost

An undercharged shipper is the most common cause of a failed cryogenic transport, and it is entirely preventable.

The absorbent matrix has to be fully saturated, which takes appreciably longer than most protocols allow. The vessel must then be inverted and drained so that no free liquid remains, because free nitrogen changes both the vessel’s regulatory position and its behaviour in transit.

Weigh the unit before and after charging and record both figures. Weight is the only practical measure of how much cold mass is genuinely in the vessel and the only check that catches a matrix that has not taken a full charge. A visual inspection tells you nothing about saturation.

Charging is also the highest risk operation in the process for the people doing it. BCGA Code of Practice 30, on the safe use of liquid nitrogen dewars, records that asphyxia due to oxygen deficiency is often rapid with no prior warning to the victim. A freshly charged shipper does not share a lift with a person. Send it up and take the stairs.

Read the published hold time as a ceiling

Published hold times are measured under favourable, clearly defined conditions: upright, unopened, at moderate ambient temperature.

Real shipments meet none of those reliably. Orientation changes, ambient temperature varies considerably, customs holds happen without warning, and every opening costs hold time that cannot be recovered. Build the margin against the delay you have not planned for rather than the journey you have. A hold time quoted without the conditions under which it was measured is not a planning figure.

The documentation, stated correctly

Two provisions apply and they are constantly conflated, including across a good deal of supplier literature.

The shipper itself travels as not restricted under Special Provision A152 of the IATA Dangerous Goods Regulations, provided the packaging cannot build pressure or release nitrogen in any orientation and the air waybill carries the words not restricted together with the special provision number.

Packing Instruction 650 of the same regulations governs the biological samples inside, where those are classified as UN 3373 Category B. It applies to the samples, not to the nitrogen holding them cold.

A dry shipper is not exempt from Packing Instruction 650. Packing Instruction 650 was never about the nitrogen. Getting this wrong in either direction causes the same outcome at the airport: a consignment held while somebody works out what it is.

The handovers, and how to close them

Name a contact at both ends who will be available on the day, not a department. Confirm the receiving laboratory has somewhere to put the samples before the shipper leaves, because a shipper arriving at a site with no free canister position is a shipment on a clock with nowhere to go.

Send the tracking reference and the expected arrival to the receiving contact directly rather than relying on the courier’s notification. Tell them the hold time and the date it expires, in writing, so that a delay becomes a decision rather than a discovery.

And record the weight on arrival if you can. It is the one measurement that tells the receiving laboratory whether the shipment still had margin or was close to the edge, and it is the only feedback that improves the next shipment.

For Certificates of Analysis, customer traceability requirements or help sizing a shipper to a specific route and format, speak to Cryolab.