Class 2 covers gases, and the sub-division that causes the most everyday confusion is Division 2.2, the non-flammable, non-toxic gases. If you are searching for class 2.2 dangerous goods, you are usually shipping a cylinder: carbon dioxide for a drinks dispenser, compressed oxygen for a medical kit, a fire suppression bottle, a nitrogen cylinder for a laboratory. Each looks harmless on the bench. Each is regulated, and the classification decides how it moves by ground, air and ocean.
This post works through the classification using real output from the Classify7 engine. You will see what a determination includes, what it leaves open, and where the carrier rules start to bite. The examples come from ruleset version 2026.08.1, and they reproduce from the same plain-text inputs.
What class 2.2 dangerous goods means
The base definition sits in 49 CFR 173.115. Division 2.2 covers a non-flammable, non-poisonous compressed gas, including compressed gas, liquefied gas, pressurised cryogenic gas, compressed gas in solution, asphyxiant gas and oxidising gas. The test is a gauge pressure of at least 200 kPa in the packaging at 20 degrees Celsius, or the material is a liquefied gas or cryogenic liquid, and it is not a Division 2.1 or 2.3 material.
Two things follow from that wording. First, the test is about the gas as packaged. Second, the exclusions matter as much as the inclusion. A flammable gas is 2.1 and a toxic gas is 2.3, so 2.2 is the residual case only once both have been ruled out. A cylinder of flammable gas that is classed as 2.2 on the basis of its pressure alone would be a misclassification, and it is one of the errors that shows up when teams work from a product name instead of a composition.
A caution on the numbers. Older summaries of the pressure test quote a figure in absolute kilopascals, and the wording has moved over time. Check the current eCFR text before you copy a threshold into a compliance file. The PHMSA interpretations are worth reading as well: a 2018 PHMSA letter (reference 18-0031) concluded that a liquefied gas meeting the liquefied-gas condition is a Division 2.2 material regardless of the pressure test.
Gases have no packing group
Packing groups I, II and III describe degree of danger for the classes that carry one. Gases do not. A 2.2 entry has a UN number, a proper shipping name, a class and often a subsidiary risk, but no packing group. Our guide to packing groups I, II and III explains where the rating does apply.
The practical effect is that a document which shows a packing group against a 2.2 cylinder is wrong, and a team that fills one in because the template expects it has introduced an error. Leave it blank and say why.
A worked example from the engine
We passed three plain product descriptions through the classifier, exactly as the API receives them. No composition, no SDS, no UN number was supplied, so the engine had to find the entry itself.
| Input description | Determination | UN number | Proper shipping name | Class and subsidiary | ERG guide | Special provisions |
|---|---|---|---|---|---|---|
| Carbon dioxide cylinder, 6 kg, compressed gas for beverage dispensing | Classified | UN1013 | Carbon dioxide | 2.2, no subsidiary | 120 | T50 |
| Compressed oxygen cylinder, medical, 2 litre | Classified | UN1072 | Oxygen, compressed | 2.2, subsidiary 5.1 | 122 | A14 |
| Nitrogen compressed gas cylinder, 10 litre | Needs review | None | None | None | None | None |
Three things stand out. The two classified results land on the specific entries a shipper needs, UN1013 and UN1072, rather than on a generic gas entry. The oxygen result carries the oxidiser label and the 5.1 subsidiary risk, so the label set on the package is the same as the one the document should show. And both classified results report limited quantity eligibility as false, which means the relief many e-commerce teams assume will not carry these cylinders.
The nitrogen result is the one to pay attention to. The engine did not choose the nearest-looking entry. It returned needs review, a null UN number and a request for more description. The engine also returns the hazmat flag as null rather than false in that case, because an unknown is not the same as not regulated. A system that says "not dangerous" when it has not decided is the one that gets a shipper into trouble, so this is the behaviour to look for in any tool you use.
Where the carrier rules bite
Classification answers whether the gas is regulated. It does not answer whether a given carrier will take it. For both class 2.2 dangerous goods examples that classified, the engine returned the same carrier picture:
- UPS: contract-required for ground and for air.
- FedEx: contract-required for ground and for air.
- USPS: restricted for ground, prohibited for air.
- Amazon FBA: review-required for ground, restricted for air.
This is the pattern that surprises people with cylinders. The regulation says the consignment may be shipped under conditions, and the carrier says it needs a contract, a review or a prohibition before the parcel moves. A determination that stops at the UN number has done the hard part and missed the part that decides whether the cylinder leaves the building. Our comparison of dangerous cargo classification across UPS, FedEx and USPS sets out the integrator side in more detail.
Cylinders are a separate compliance file
Most 2.2 consignments are cylinders, and the cylinder itself is regulated. Packing Instruction 200 governs cylinders. An ICAO working paper reproduces its special provisions, which forbid aluminium alloy cylinders and copper valves, and cap the copper content of wetted metal parts at 65 per cent. Steel or composite cylinders with steel liners must bear an H mark to be accepted.
The same material notes that refillable cylinders must be periodically inspected under PI 200. A cylinder past its inspection date may not be refilled, but it may still be transported after the time limit has passed. Keep the inspection date on the same record as the classification, because a cylinder that is correctly classed can still be the wrong cylinder to ship.
The classification tells you which rules apply. The cylinder, its inspection date and the carrier's current acceptance tell you whether the consignment can move today.
Classify7 ruleset team, on why 2.2 cylinders are checked on three axes
A checklist for Division 2.2 shipments
- Confirm the gas is non-flammable and non-toxic before you treat it as class 2.2 dangerous goods. A flammable or toxic gas belongs elsewhere.
- Identify the specific entry. Carbon dioxide is UN1013, compressed oxygen is UN1072 with a 5.1 subsidiary, and neither should go out under a generic gas description.
- Record the subsidiary risk and the labels, not just the class.
- Leave the packing group blank and state that gases have none.
- Check the cylinder against PI 200 and its inspection date.
- Check carrier eligibility for each lane. A contract-required result means you need the contract before the first shipment.
- Store the ruleset version with the determination, so you can tell later which criteria produced it.
- Assigning 2.2 from the product name without checking whether the gas is also flammable or toxic.
- Using a packing group on a gas document because the template expects one.
- Treating a needs-review result as not regulated.
- Assuming limited quantity relief applies to a cylinder that is classed 2.2.
- Checking the UN number and skipping the carrier overlay for the lane you actually use.
Related guides
For the dry-ice case, which has its own entry and its own rules, see our dry ice dangerous goods classification guide. For the full class list and where 2.2 sits among the others, read the nine classes of hazardous materials, explained. If you ship by air, the IATA DGR 2026 edition changes post covers what moved this year. The regulation itself is at 49 CFR 173.115, and the air-transport edition is published by IATA.
