For USPS, confirm mailability and the actual transport route before packing dry ice. Packaging Instruction 9A prohibits dry ice in international mail and limits domestic air mail to 5 lb per mailpiece. Surface mail has different preparation and routing requirements. Build the packing checklist around the accepted category.
Confirm the category before assembling the box
Identify the contents, destination, postal service and permitted coolant amount. Do not substitute a passenger-baggage allowance or a commercial air-cargo checklist for USPS instructions.
Use USPS Packaging Instruction 9A with the relevant Publication 52 mailability provisions. Confirm that the contents are accepted as well as the dry ice; refrigerant permission does not make otherwise restricted contents mailable.
Prepare the tested physical configuration
- Bring the payload to its specified dispatch condition.
- Use the container intended for the particular dry-ice application.
- Load the actual dry-ice mass and form specified by the accepted packout.
- Keep separators and payload positions consistent with that configuration.
- Use suitable containment for the contents without making a sealed CO₂ vessel.
- Protect the mailing carton against moisture and physical damage.
The assembled package must release CO₂ gas. Preserve that feature during closure and outer protection. Thermal insulation and gas release must coexist; taping every opening indiscriminately is not an approved packing method.
Use the route-specific postal checklist
| Route | Preparation distinction |
|---|---|
| Domestic air | Observe the 5 lb limit and the air marks, Class 9 label and triplicate declaration specified by 9A. |
| Domestic surface | Use the required surface-only marks and ensure the mailpiece is not routed by air. |
| International mail | Do not prepare a USPS international parcel containing dry ice. |
Instruction 9A requires contents and net dry-ice weight information on the address side. Review the exact current marking and document requirements at dispatch rather than relying on a preprinted template alone.
Reconcile the final parcel before handoff
Check the actual loaded quantity, marks, labels and documents together. Confirm that no outer component hides required information or obstructs gas release. Keep the packing instruction and the current postal category in the same dispatch record.
Helpful decision tools
Check the details before you choose packaging
These quick tools can help you compare route risk, sizing needs, coolant choices, and packaging details before you request a quote.
Box Liner & Pallet Cover Sizing
Check box liner and pallet cover sizing logic for insulated packaging projects.
Estimate sizingIce Pack Calculator
Estimate gel ice pack quantity for chilled shipments and practical route planning.
Estimate ice packsCoolant & PCM Reference
Compare coolant and PCM options when a route needs added temperature support.
Compare optionsConfirm collection and recipient arrangements. The complete exposure runs from packing to appropriate receiving storage, not just the scheduled movement between postal facilities. A correctly marked parcel can still have inadequate thermal performance.
Frequently asked questions
Can I use more than 5 lb and still choose domestic air?
No. That exceeds the dry-ice limit stated by USPS for domestic air mail.
Can I copy a cargo declaration exemption into USPS air mail?
No. Follow the postal-specific requirements, including the declaration required by Instruction 9A.
Is an approved label enough to prove the food stayed frozen?
No. Mailing acceptance and payload temperature performance need separate evidence.
Keep scope and execution separate
For marking applicability, see the dry ice shipment scope guide. For service and thermal planning, use the Priority Mail Express cold-chain guide. This checklist focuses on preparing the accepted parcel for dispatch.
