Shipping With Dry Ice (UN 1845): Air, Sea and Road Rules Explained

Dry ice is solid carbon dioxide, listed as UN 1845 and classed as Class 9 (miscellaneous dangerous goods). It is the standard refrigerant for frozen samples, vaccines, seafood and meal kits, and it is regulated not because it is flammable or toxic but because it turns into gas as it warms. That gas can burst a sealed package and can displace the oxygen in a closed cargo space. The practical takeaway: never seal dry ice airtight, always mark the net weight, and expect each mode to ask for something different. By air, dry ice used to cool ordinary goods usually needs no Shipper's Declaration, but it still needs marking, an airline arrangement and a specific waybill entry. This guide covers the rules as published by the US regulations, ICAO and the IMDG Code as of October 2026; it sits alongside our guides on active vs passive cold chain packaging and the nine dangerous goods classes.

Why is dry ice dangerous goods?

Dry ice does not melt. It sublimates, going straight from solid to gas at roughly minus 78 degrees Celsius. Two hazards follow, and both are why the rules insist on venting.

• Pressure build-up. A sealed container, cooler or bottle holding dry ice can rupture. That is why the US rule (49 CFR 173.217(a)) requires packagings "designed and constructed to permit the release of carbon dioxide gas to prevent a buildup of pressure that could rupture the packagings".
• Asphyxiation. CO2 is heavier than air (BAM, the German federal materials-testing institute, gives a relative density of 1.5 in its IMDG data) and can cause unconsciousness when inhaled. In December 2020 the FAA's Safety Alert for Operators 20017 warned that CO2 from sublimating dry ice can displace oxygen in aircraft compartments, and that the risk rises with the amount of dry ice, its sublimation rate and any loss of ventilation.

What do the rules require, mode by mode?

There is no single global rulebook. Air follows the ICAO Technical Instructions, which IATA turns into the Dangerous Goods Regulations (DGR). Sea follows the IMDG Code. Road follows national or regional law: ADR in Europe, the US Hazardous Materials Regulations (49 CFR) in the United States. The table compares them. The full IATA DGR and IMDG Code texts are paid publications, so where this guide relies on a published summary rather than the code itself, it says so.

Shipping dry ice by air: Packing Instruction 954

Packing Instruction 954 is the air instruction for UN 1845. According to the ICAO Technical Instructions 2025-2026 summary published by BAM, it applies to both passenger and cargo aircraft, with a maximum of 200 kg net per package, and intermediate bulk containers are not permitted. That summary lists no limited-quantity or excepted-quantity exemption for dry ice. Individual airlines can impose stricter limits (operator variations), so treat 200 kg as a ceiling and not a promise that a carrier will accept it.

The points that matter in practice:

• Venting. The packaging must let CO2 escape. Insulated boxes with a loose lid or vent path are normal. A cooler taped shut is not.
• Marking. The US rule requires the net mass of the dry ice on the outside of the package (49 CFR 173.217(c)(1)). Carrier and university guides for air shipments also list UN 1845, the proper shipping name ("Dry ice" or "Carbon dioxide, solid") and the Class 9 label. For an overpack, they say the total net weight goes on the outside of the overpack.
• Airline arrangement. The shipper must make arrangements with the operator for each shipment (49 CFR 173.217(c)(2)). Do not tender dry ice to an airline that has not agreed to carry it.
• Documents. When dry ice is only refrigerating non-dangerous goods, a Shipper's Declaration is generally not required. Instead the air waybill (or equivalent document) must carry the dry ice details. The US rule lists them in 49 CFR 173.217(c)(4): the proper shipping name, Class 9, UN 1845, the number of packages and the net quantity of dry ice in each package. Compliance guides summarising IATA DGR describe the same entry in the "Nature and Quantity of Goods" box.

A common misconception: "No declaration means no paperwork." It does not. The waybill entry is the paperwork, and a missing or wrong entry is a common reason for a refusal at acceptance.

If the dry ice is refrigerating other dangerous goods, the shipment is a dangerous goods shipment in its own right. For example, a frozen Category B biological sample falls under its own packing instruction, with dry ice added to it. Follow our dangerous goods declaration guide and check the DGR for how the dry ice is declared alongside the primary goods.

Dry ice in unit load devices

Large shipments often go as a whole ULD. The US rule lifts the per-package limits for dry ice used as a refrigerant for non-hazardous contents in a ULD, but the ULD must be identified to the operator and must vent the CO2 (49 CFR 173.217(c)(3)); ICAO special provision A151 says the same. Summaries of IATA DGR section 5.9 add that such a ULD generally cannot also hold other dangerous goods, and that the waybill then gives the ULD identification and net dry ice quantity. Check the current DGR for the wording.

Is there a small-quantity exception?

In the US, yes: dry ice up to 2.5 kg (5.5 lb) per package, used as a refrigerant for the contents, is excepted from the other requirements if the package is vented and marked "Carbon dioxide, solid" or "Dry ice", with the name of the contents and the net weight (or a statement that it is 2.5 kg or less) (49 CFR 173.217(c)(5)). Some older guidance quotes 2.3 kg; the current text says 2.5 kg, so check the live eCFR. It is a US rule and does not travel: for international air freight the ICAO instruction applies, and I found no equivalent exception in the ICAO summary. Ask the airline.

Shipping dry ice by sea: the IMDG Code

At sea there are two different situations, and mixing them up causes most of the errors.

1. Dry ice as a coolant inside a container. Section 5.5.3 of the IMDG Code covers cargo transport units that use dry ice for cooling or conditioning. According to BAM's IMDG data (Amendment 42-24), such a unit is exempt from the other IMDG provisions, except fumigation, but only the dry ice benefits: any dangerous goods loaded into the same unit must still meet every applicable rule. Packages must withstand very low temperatures and allow gas to vent, the load must be secured so it cannot shift once the ice sublimates, and unpacked dry ice must be kept at least 30 mm from the metal structure of the unit. People who handle these units must be trained.
2. Dry ice as the cargo itself. Section 5.5.3 does not apply when the substance is shipped as a consignment of dangerous goods. It then travels as Class 9, UN 1845, with the full IMDG treatment.

For the first case, the container needs a warning sign at every access point, kept in place until the unit has been ventilated and the cooled goods unloaded. BAM's summary describes a rectangular sign of at least 150 mm by 250 mm, with "WARNING" and the agent's name ("CARBON DIOXIDE, SOLID") in capitals. If the unit was not fully ventilated before transport, the shipping paper should carry the UN number and the name followed by the coolant wording, for example "UN 1845, CARBON DIOXIDE, SOLID, AS COOLANT". Packages carry the technical name followed by "as coolant" or "as conditioner".

Because the underlying provisions are in the IMDG Code text, confirm the exact sign dimensions, wording and documentation against the amendment in force on your sailing date. Our guide to the IMDG Code and IATA regulations explains how the two rulebooks fit together, but it is not a substitute for the code itself.

In the US, 49 CFR 173.217(b) separately requires freight containers and transport vehicles holding solid carbon dioxide to be marked on two sides "WARNING CO2 SOLID (DRY ICE)", and other packagings marked "CARBON DIOXIDE, SOLID" followed by "DO NOT STOW BELOW DECKS".

Shipping dry ice by road

In Europe, ADR section 5.5.3 mirrors the IMDG approach. The BAM ADR entry for UN 1845 says packages must allow gas release and withstand low temperature, and the warning mark is not needed where the vehicle or container is well ventilated, which the entry defines as CO2 below 0.5 vol% and oxygen above 19.5 vol%. A closed van with no airflow is the case that needs the sign.

In the United States, the UN 1845 entry carries the "A" and "W" symbols in the Hazardous Materials Table, which under 49 CFR 172.101 means it is subject to the regulations only when offered for transportation by aircraft or vessel. A PHMSA interpretation letter (12-0223) on highway shipments of dry ice turns on those symbols. Even so, a vented package, a ventilated cargo area and driver awareness are basic safety, and carriers often have their own acceptance rules.

How long will the dry ice last? A note on sublimation

There is no universal formula. The best public data point is an FAA study (DOT/FAA/AM-06/19, 2006) that put about 5 lb of pelletised dry ice in each of 20 shipping containers and held them at 8,000 ft in an altitude chamber for a simulated six-hour flight. The average loss was 2.0 percent of the dry ice per hour (plus or minus 0.3), and pellets sublimated faster than a single block.

Read that as one test condition, not a planning rule. Insulation, ice shape, temperature and cabin pressure all change the rate. To size dry ice for a real lane, run a packaging qualification with a data logger and add a margin for delay. Loggers usually contain lithium cells, so check the lithium battery rules if you ship them separately.

Dry ice shipping checklist

• Is the dry ice cooling only non-dangerous goods? If not, the full dangerous goods route applies.
• Packaging is insulated and designed to vent, never airtight.
• Net weight of dry ice in kilograms is marked on the outside, with UN 1845, the proper shipping name and the Class 9 label where the mode requires them.
• The airline has agreed to carry it, and has confirmed its own limit and any variation.
• The air waybill or equivalent states UN 1845, the proper shipping name, Class 9, the number of packages and the net quantity per package.
• For containers: ventilation plan, warning sign on each access point, and the coolant wording on the shipping paper where required.
• Staff who pack, load and open the unit are trained and know not to enter an unventilated container.
• Enough dry ice for the planned transit plus delay, proven by a qualification run and a temperature logger.

What to do next

1. Decide the mode and whether the dry ice is a coolant or the cargo, then pick the matching rulebook (PI 954, IMDG 5.5.3 or ADR 5.5.3).
2. Ask the airline or shipping line for their dry ice acceptance rules and any limit below the regulatory ceiling.
3. Build one sample pack, ship it on the real lane with a logger, and weigh the ice at the start and end.
4. Write the waybill or shipping paper entry and the package marks from a template so every consignment uses the same wording.

If you need a forwarder that handles temperature-controlled or dangerous goods freight, you can search more than 29,300 logistics companies by country and service in the CargoLinked directory, or post your shipment on the public requests board, which lists freight that shippers have posted for forwarders to quote on directly. State the dry ice and its net weight in the request.

This article is general information, not legal or regulatory advice. Dry ice rules are set by ICAO, IATA, the IMO and national authorities and change between editions, and airlines and shipping lines may apply stricter rules. Confirm every shipment against the current regulations and with the carrier, or with a qualified dangerous goods adviser, before you ship.