Dry ice is officially classified as a hazardous material for shipping purposes, but it falls into the lowest-risk category. The U.S. Department of Transportation assigns it Class 9 (Miscellaneous Hazardous Material) under UN number 1845. In practice, this means dry ice carries fewer regulatory burdens than most hazmat substances, with several key exemptions that make it relatively simple to ship and transport.
How Dry Ice Is Classified
Class 9 is the catch-all category for materials that pose a transport risk but don’t fit neatly into the more dangerous classes like flammables, explosives, or toxic substances. Dry ice lands here because it sublimates into carbon dioxide gas, which can displace oxygen in enclosed spaces and cause pressure buildup in sealed containers. Those two properties, asphyxiation risk and pressure risk, are why it gets the hazmat label at all.
The classification applies specifically to transport. Buying dry ice at a grocery store or using it in a cooler at home doesn’t involve hazmat regulations. The rules kick in when you put it in a package and hand it to a carrier, load it onto an aircraft, or transport it commercially by road.
What the Rules Require for Shipping
Dry ice gets a meaningful break from standard hazmat paperwork. Under federal regulation (49 CFR 173.217), it’s exempt from the formal shipping paper requirements that apply to most hazardous materials. Instead, you need alternative written documentation that includes the proper shipping name (“Dry ice” or “Carbon dioxide, solid”), the Class 9 designation, UN1845, the number of packages, and the net weight of dry ice in each package. No formal Shipper’s Declaration for Dangerous Goods is required when dry ice is the only regulated item in the shipment.
Your outer packaging must be marked with “Dry ice” or “Carbon dioxide, solid,” the UN1845 number, the net weight in kilograms, and both the shipper’s and recipient’s addresses. Despite being a hazmat item, dry ice has no labeling requirements under the Hazardous Materials Regulations for ground transport. For air shipments through carriers like FedEx, you will need a Class 9 Miscellaneous Hazard label on the package.
Ground vs. Air Transport
The rules differ significantly depending on how your dry ice travels. For ground shipping, regulations are lighter. FedEx, for example, doesn’t regulate dry ice as hazardous material on its ground service at all. You still need to mark the package as containing dry ice and notify the driver at pickup, but the full hazmat procedures don’t apply. FedEx charges a $5.90 dry ice surcharge on non-dangerous-goods shipments sent by air.
Air transport is stricter. The FAA limits passengers to 2.5 kilograms (5.5 pounds) of dry ice per package, whether in carry-on or checked baggage, and it must be used to pack perishables. Checked bags containing dry ice need to be marked with “Dry ice” or “Carbon dioxide, solid” and show the net quantity. The package cannot be sealed airtight, since the sublimating gas needs somewhere to go.
If your company ships dry ice by air regularly, employees who prepare those shipments need dangerous goods training. This is a carrier requirement across FedEx, UPS, and other major shippers.
Packaging Requirements
The single most important rule for packaging dry ice is ventilation. As it warms, dry ice converts directly from solid to gas, expanding roughly 800 times in volume. A sealed, airtight container can explode. Every package must allow carbon dioxide gas to escape gradually.
In practical terms, this means using styrofoam shipping containers inside cardboard outer boxes, and never taping them completely airtight. Secure the tape enough that the box won’t open in transit, but leave gaps for gas to vent. Never put dry ice in a jar with a threaded lid, a sealed plastic cooler, or any container with an airtight closure. Some plastics become brittle at the extreme cold temperatures of dry ice (around negative 78.5°C), so commercially available dry ice shipping containers are the safest option.
The outer package also needs to be strong enough to handle normal loading and unloading without losing its contents due to vibration, altitude changes, or temperature shifts.
Why Dry Ice Is Considered Hazardous
Two real dangers drive the classification. First, carbon dioxide gas displaces oxygen. In a poorly ventilated space like a vehicle cabin, walk-in freezer, or small room, sublimating dry ice can push CO2 concentrations to dangerous levels. OSHA sets the permissible workplace exposure limit for carbon dioxide at 5,000 ppm over an eight-hour period, with a short-term ceiling of 30,000 ppm. A few pounds of dry ice in a closed car can exceed those thresholds surprisingly fast. Dry ice sublimates at roughly 3% to 8% of its mass per day under normal conditions, but that rate increases with warmer temperatures and more surface area exposed to air.
Second, direct skin contact causes cold burns similar to frostbite. OSHA recommends cryogenic gloves designed for temperatures below negative 80°C, and they should be loose-fitting so you can pull them off quickly if a piece of dry ice falls inside. Eye protection is also recommended whenever you handle dry ice.
What This Means for You
If you’re shipping a package with dry ice through a major carrier, you need proper markings on the box and documentation showing the weight, but you’re unlikely to face the full hazmat shipping process that applies to truly dangerous chemicals. Ground shipments are the simplest. Air shipments require a few more steps, including weight limits and a Class 9 label.
If you’re a business shipping dry ice regularly, your employees need training, and you should use purpose-built shipping containers. If you’re an individual sending a cooler of frozen steaks to a relative, you’ll follow the same marking rules but won’t need a formal dangerous goods declaration. The hazmat classification exists primarily because of the asphyxiation and pressure risks during transport, not because dry ice is inherently toxic or reactive. Handle it with gloves, keep it ventilated, and label your packages correctly.