Quick answer
A dry shipper is a vacuum-insulated cryogenic shipping container whose inner lining absorbs liquid nitrogen. After charging, it holds no free liquid, yet the trapped nitrogen keeps the sample chamber at −150°C or colder for days. Because it cannot spill or build pressure, a properly prepared dry shipper flies as “not restricted” under IATA Special Provision A152.
Key takeaways
- “Dry” means no free-flowing liquid nitrogen, not “less cold.” The absorbent core holds liquid nitrogen (it boils at −196°C) and releases ultra-cold vapor.
- Samples sit in nitrogen vapor at −150°C or colder, well below the range where vitrified eggs and embryos are at risk.
- Hold time depends on the model, the charge and the handling. Plan routes around real-world hold time, not the brochure maximum.
- A correctly charged dry shipper is not regulated as dangerous goods for air transport. Free liquid nitrogen and dry ice are.
- A temperature data logger turns “we kept it cold” into a record both clinics can check.
When frozen embryos, eggs or sperm move between clinics, they almost always travel in a dry shipper. Outside, it is a plain aluminum canister. Inside, it is a balanced system of absorbent chemistry, vacuum insulation and nitrogen vapor. Here is how it works, how long it stays cold, and why airlines accept it as ordinary cargo.
What is a dry shipper?
The U.S. Federal Aviation Administration defines a dry shipper as “an insulated cryogenic flask/container that contains refrigerated liquid nitrogen absorbed into a porous lining,” used to transport specimens (FAA PackSafe). You will also see the terms vapor shipper, cryoshipper, cryo shipper, LN2 dry shipper and dry shipper container. All describe a dewar built for travel rather than storage.
Dry shippers are used wherever a sample must stay cryogenic outside the lab: IVF and fertility preservation (sperm, oocytes, embryos), stem cells, research cell lines and animal breeding, where a dry shipper for semen is standard equipment.
How a dry shipper works with liquid nitrogen
Three pieces of engineering work together.
1. The absorbent core
The inner chamber is lined with a porous, hydrophobic absorbent. During charging, the chamber is filled with liquid nitrogen for the manufacturer’s recommended time while the absorbent soaks it up; the excess free liquid is then poured off. The nitrogen that remains is held inside the pores, not sloshing around, and slowly boils into cold gas that fills the sample space.
2. Vacuum insulation
A double wall with a vacuum between the layers, the principle James Dewar used in the original dewar flask, stops most heat transfer by conduction and convection. The main heat path is the narrow neck, which is why dry shippers have long, slim necks and insulated plugs. The lid is deliberately not airtight: nitrogen gas must escape, and the FAA notes it is normal to see some vapor.
3. Vapor-phase storage
Straws, vials or goblets sit in a canister within the nitrogen vapor, never submerged in liquid, so there is no shared liquid bath to carry contaminants between samples. Vapor phase is well studied in IVF: in a prospective randomized study, vitrified human oocytes stored long-term in nitrogen vapor versus liquid nitrogen showed survival of 95.3% vs 94.5%, with similar fertilization, embryo development and pregnancy rates (Cobo et al., Fertility and Sterility, 2010). That study examined storage tanks, not shipping, but it shows the vapor phase itself is not a compromise when temperature is controlled.
Why both −196°C and −150°C matter
Liquid nitrogen boils at −196°C; the vapor around the samples is slightly warmer. Correctly prepared dry shippers keep specimens at −150°C or colder (Harvard EHS). For vitrified eggs and embryos, the key threshold is the glass transition of the vitrification solution. One laboratory study measured it between −126°C and −121°C, with devitrification starting around −109°C, and warned that samples handled in warmer vapor can reach critical temperatures within about 30 seconds (Sansinena et al., Theriogenology, 2014). The shipper keeps a wide safety margin; the riskiest moments are transfers in and out of it, which must be fast.
Hold time and evaporation rate: how long does a dry shipper stay cold?
| Term | What it means | Why it matters |
|---|---|---|
| Static evaporation rate | Liters of liquid nitrogen lost per day with the shipper upright, lid closed, in stable room conditions | The baseline “fuel consumption” of the unit |
| Static hold time | Roughly the absorbed nitrogen capacity divided by the static evaporation rate | The best case, measured in the lab |
| Dynamic hold time | How long the shipper stays cryogenic in real transit, with movement, tilting and temperature swings | Always shorter than static; the number routes should be built on |
A real example: the MVE SC 4/2V, one of the models on our dry shipper page, holds 3.6 liters of liquid nitrogen, evaporates 0.26 liters per day and has a normal working duration of 14 days (3.6 ÷ 0.26 ≈ 13.8).
In practice, hold time shrinks when the shipper is tilted or laid on its side, when the lid is opened repeatedly, when it sits in heat, when it was not fully charged, or when the vacuum has degraded (frost or condensation on the outer wall is a warning sign). A well-planned international route leaves days of margin for customs holds, missed connections and weekends.
Why a dry shipper doesn’t spill
With the nitrogen locked in the absorbent and the excess drained, there is nothing free to pour out. The FAA’s conditions spell it out: the liquid nitrogen must be completely absorbed with no free liquid, the container must not allow pressure build-up, and nitrogen must not escape regardless of orientation. Professional couriers still keep shippers upright; ARK.CRYO transports dewars vertically only, because orientation affects hold time even when it does not affect safety.
Dry shipper vs dewar vs dry ice shipper
| Dry shipper | Liquid nitrogen storage dewar | Dry ice shipper | |
|---|---|---|---|
| Coolant | Liquid nitrogen absorbed in a porous core | Free liquid nitrogen | Solid carbon dioxide |
| Temperature | −150°C or colder (vapor phase) | −196°C (in the liquid) | About −78.5°C |
| Free liquid inside? | No | Yes | No (it turns into gas) |
| Air transport status | “Not restricted” under Special Provision A152 when conditions are met | Dangerous goods (UN 1977, refrigerated liquid nitrogen) | Dangerous goods (UN 1845), declared and packaged per the rules |
| For frozen eggs, embryos, sperm? | Yes, the standard for transport | Yes, for storage at the clinic or bank | No, too warm |
Dewar vs dry shipper. “Dewar” is the umbrella term for any vacuum-insulated cryogenic vessel. A liquid nitrogen dewar in a clinic holds free liquid and is built for long-term storage. A dry shipper is a dewar engineered for travel.
Liquid nitrogen vs dry ice. Dry ice works for many frozen pharmaceuticals, but at about −78.5°C it sits far above the −109°C point where devitrification of vitrified samples can begin. It is also regulated as dangerous goods that must be properly declared and packaged (NIH Division of Occupational Health and Safety). For reproductive cells, a dry ice shipper is no substitute for a liquid nitrogen dry shipper.
Is a dry shipper dangerous goods? What IATA and the FAA say
Free liquid nitrogen is regulated as UN 1977, refrigerated liquid nitrogen. A dry shipper is treated differently: the IATA Dangerous Goods Regulations list “insulated packagings containing refrigerated liquid nitrogen (dry shipper), fully absorbed in a porous material containing only non-dangerous goods” as a separate entry (IATA DGR, Table 2.3.A). Under Special Provision A152, such packagings are not subject to the regulations when the design prevents pressure build-up and any release of liquid nitrogen in any orientation. The air waybill must state verbatim: “Not restricted, as per Special Provision A152” (Harvard EHS).
- The exemption covers the shipper, not everything inside it. If the contents were themselves regulated, for example infectious substances, other rules would apply.
- Preparation is part of compliance. A shipper with free liquid left inside no longer meets the conditions, so every dispatch needs a documented absorption check.
Security screening is a separate question. At ARK.CRYO, reproductive cells never pass through X-ray.
Temperature data loggers: the shipment’s flight recorder
A dry shipper keeps samples cold; a data logger proves it. The logger records the internal temperature at set intervals, so on arrival the embryologist can check the full time-temperature curve instead of trusting a label. ARK.CRYO fits temperature loggers on all of its equipment. More in temperature-controlled shipping explained.
Preparing a dry shipper: a checklist
- Inspect the unit: no dents, no frost or sweating on the outer wall, intact neck plug and case.
- Charge for the manufacturer’s full recommended time.
- Pour off excess liquid and verify there is no free liquid nitrogen, as the manufacturer specifies.
- Pre-cool the canister, then load samples quickly.
- Start and attach the temperature data logger.
- Close with the vented lid, pack in the transport case, mark orientation and add the A152 statement to the air waybill.
- Plan handovers around dynamic hold time, with a margin for delays.
Preparing the shipment itself? See how to ship sperm safely and how long embryos can stay frozen.
How ARK.CRYO uses dry shippers
For 10 years, ARK.CRYO has moved reproductive and cellular material across 80+ countries on 5 continents, with 4,500+ successful shipments.
- IATA-compliant dry shippers such as the MVE SC 4/2V, MVE SC 2/1V and Taylor Wharton CX100, in full compliance with IATA standards.
- Temperature loggers on all equipment, so both clinics see the full temperature record.
- Onboard personnel: an ARK.CRYO team member accompanies the dewar on board.
- X-ray free: reproductive cells never go through X-ray screening.
- 24/7 legal and customs support for export and import documents.
Our work was featured on The Tamron Hall Show as part of Jessel Taank’s IVF journey; Peter Hura was shortlisted at the Fertility Care Awards 2025; and ARK.CRYO took part in ASRM 2025. We work with 20+ partners, including Men Having Babies, Ovogene, International Fertility Group, California Cryobank and Shady Grove Fertility. Read client reviews or learn more about our team.
Moving embryos or eggs? See embryo shipping and our IVF shipping services. Comparing providers? Our guide on how to choose a cryo shipping company lists the questions to ask about their dry shippers.
FAQ
What is a dry shipper?
A dry shipper is a vacuum-insulated container whose lining absorbs liquid nitrogen. It holds no free liquid, yet keeps samples at −150°C or colder. It transports frozen sperm, eggs, embryos, stem cells and other samples and, when correctly prepared, is not treated as dangerous goods on aircraft.
How long does liquid nitrogen last in a dry shipper?
It depends on the model, the charge and the handling. Manufacturers publish a static hold time measured in the lab; the MVE SC 4/2V, for example, lists 0.26 liters per day and about 14 days. Real-world hold time is shorter, so routes need a safety margin.
Is a dry shipper hazardous for air transport?
Not when prepared correctly. Under IATA Special Provision A152, a dry shipper with nitrogen fully absorbed, no pressure build-up and no leakage in any orientation is not subject to the Dangerous Goods Regulations. The air waybill must state “Not restricted, as per Special Provision A152.”
What is the difference between a dewar and a dry shipper?
“Dewar” is the general name for a vacuum-insulated cryogenic vessel. A storage dewar holds free liquid nitrogen at −196°C for long-term storage. A dry shipper is a dewar designed for travel: the nitrogen is absorbed, nothing can spill, and samples sit in vapor at −150°C or colder.
Can I use dry ice instead of a liquid nitrogen dry shipper?
Not for cryopreserved eggs, embryos or sperm. Dry ice is about −78.5°C, well above the −109°C point where devitrification of vitrified samples can begin, and it is regulated as dangerous goods. It suits many frozen pharmaceuticals, but reproductive cells need liquid nitrogen.
What is an empty dry shipper?
The term covers two cases: a shipper that is uncharged or has run out of nitrogen, and a charged shipper travelling without samples, for example to a clinic for pickup. An uncharged unit is simply an insulated container; a charged one follows the same A152 conditions as a loaded one.
What is the advantage of a dry shipper?
It combines cryogenic temperatures with safe air transport. Samples stay at −150°C or colder for days, there is no free liquid to leak or build pressure, samples never share a liquid bath, and a correctly prepared unit travels as non-restricted cargo.
How much does it cost to ship with a dry shipper?
Shipment price depends on route and distance, the type of material, customs and permit requirements, courier accompaniment and timing. The dry shipper is part of the service, not a separate purchase. For current terms, see pricing and delivery terms or request a quote.
Ready to ship?
Tell us what you are shipping, from where and to where, and our team will plan the route around a dry shipper and its real hold time. Request a delivery or call USA +1 888 761 5820, Europe +421 233 215 889.
