Dry ice dangerous goods classification catches out more food and pharma shippers than any other Class 9 entry, for one reason: it does not feel like a dangerous good. It is the packaging, not the product. It is there to keep the ice cream frozen.
The regulations do not care what it is there for. Dry ice is UN1845, hazard class 9, and it is regulated in every mode. This guide covers what that actually requires, where the limits sit, and the marking that gets left off.
Why frozen CO₂ is regulated at all
Dry ice is solid carbon dioxide at about −78 °C. It does not melt — it sublimates, going straight from solid to gas. That single property creates both hazards.
The first is asphyxiation. Carbon dioxide gas is denser than air and displaces oxygen. In an enclosed space (a van, a cargo hold, a cold room), a sublimating consignment can build a genuinely dangerous atmosphere at floor level, without smell or visible warning.
The second is pressure. One kilogram of dry ice produces roughly half a cubic metre of gas as it sublimates. Seal that in an airtight container and you have built a pressure vessel. This is why every dry ice requirement, in every mode, insists on packaging that vents.
The dry ice dangerous goods classification itself
| Field | Value | Note |
|---|---|---|
| UN number | UN1845 | Same across 49 CFR, IATA DGR and IMDG |
| Proper shipping name | Carbon dioxide, solid or Dry ice | Both are acceptable names for this entry |
| Hazard class | 9 | Miscellaneous dangerous goods |
| Packing group | None | Class 9 dry ice takes no packing group |
| Label | Class 9 | Black-and-white striped miscellaneous label |
| Air limit per package | 200 kg passenger aircraft | IATA DGR; carriers apply lower limits |
Note the packing group row. Dry ice has none. Along with lithium batteries, it is one of the Class 9 entries that sits outside the packing group system entirely, and writing "9, PG III" on a shipping paper is an error. Our guide to packing groups I, II and III covers which entries take one.
The requirement everyone forgets
Net weight marking. The outer package must show the net quantity of dry ice inside it, in kilograms.
It sounds trivial. It is the most frequently omitted dry ice requirement in parcel networks, and there is a good operational reason for the rule: a handler needs to know how much gas that box will generate. A 2 kg package and a 20 kg package present very different problems in a closed van, and nothing else on the outside distinguishes them.
The complete outer marking set is:
- Proper shipping name — "Carbon dioxide, solid" or "Dry ice"
- UN1845
- Class 9 hazard label
- Net weight of dry ice in kg
- Shipper and consignee details
When the coolant becomes the problem
A frozen meal delivery business ships insulated boxes with dry ice, and has done for two years without incident. Ground courier, sealed polystyrene liners, a foil bag over the top for temperature retention.
They expand to next-day national coverage, which means air. At the first air hub screening, consignments start failing. Three separate defects, none of which mattered on the road:
- The foil overbag made the packages effectively airtight. Venting is not optional.
- No net weight marking on any outer. Nobody had ever asked.
- Some boxes carried more dry ice than the carrier's own per-package limit for that service — well under the 200 kg regulatory figure, but over the tariff.
The product was fine. The classification was fine. The packaging and the marking, which nobody had revisited when the mode changed, were not.
Dry ice is the clearest case of a hazard that lives in the packaging rather than the product. The item being shipped can be entirely unregulated and the consignment still be a dangerous goods shipment.
Classify7 ruleset team
Working out how much dry ice you actually need
Quantity is a compliance question as well as a temperature one, because the amount you pack decides which limits and which carrier services are available to you.
Dry ice sublimates at a broadly predictable rate, driven by the insulation quality and the ambient conditions rather than by anything clever. Packing generously "to be safe" is the instinct, and it works against you three ways: it pushes you toward per-package limits, it generates more gas in the vehicle, and it costs money.
| Input | Why it matters | Where it is recorded |
|---|---|---|
| Net weight of dry ice (kg) | Drives the marking and the limit check | Outer package and air waybill |
| Transit time door to door | Determines how much sublimation to allow for | Service selection |
| Insulation performance | Sets the sublimation rate | Packaging specification |
| Carrier per-package limit | Frequently lower than the regulatory 200 kg | Carrier tariff |
| Whether it cools dangerous goods | Changes the documentation entirely | Classification of the cooled goods |
That last row is the one that changes the shape of the problem. Dry ice dangerous goods classification is straightforward when the coolant is the only regulated thing in the box. When it is refrigerating something that is itself a dangerous good (a diagnostic sample, a reactive chemical), you have two classifications and the full documentation burden of the cooled goods on top.
Carriers diverge sharply on dry ice
Dry ice is one of the entries where carrier tariffs differ more than the regulations do.
- UPS and FedEx both handle dry ice routinely on express services, with per-package limits and marking requirements set out in their own dangerous goods guides.
- USPS restricts it considerably and does not accept it on air services, which effectively removes it from most postal routes.
- Amazon applies its own conditions, and dry ice in FBA inbound is generally not a routine acceptance.
So the carrier check is not a formality here — it is frequently the binding constraint. Our carrier-by-carrier hazmat comparison sets out the positions side by side, and the carrier rules reference holds the current detail.
- Sealing the package airtight for temperature retention.
- Omitting the net weight of dry ice from the outer marking.
- Assigning a packing group to UN1845, which does not take one.
- Using the 200 kg regulatory limit when the carrier's service limit is far lower.
- Forgetting that dry ice refrigerating other dangerous goods brings the full documentation for those goods with it.
Checking a cold-chain consignment
The determination is quick because the inputs are few: is there dry ice, how much, what mode, which carrier. Send that to POST /api/classify and you get UN1845 with the class, the marking requirements and the per-carrier position for the service you intend to use.
For the wider Class 9 picture, see the nine classes of hazardous materials, or browse the encoded Class 9 entries to see what else shares the class. The regulatory text for dry ice by air sits with the IATA Dangerous Goods Regulations, and by road with PHMSA under 49 CFR.
