USPS Dry Ice Shipping In 2024: Can You Mail It, Regulations, and Best Practices
The global cold chain logistics industry is projected to grow over 8% annually, reaching $628 billion by 2026 according to Emergen Research. With demand rising, many shippers find themselves needing to transport temperature-sensitive cargo like food, medical supplies, and chemicals.
While modern shipping offers many conveniences, perishables require extra precautions – and that‘s where dry ice comes in handy as a cooling agent. But dry ice itself can also be tricky to mail properly.
Here‘s an in-depth guide examining if and how you can ship dry ice with the United States Postal Service (USPS).
Overview: USPS Dry Ice Shipping Services
USPS does permit mailing dry ice, with some restrictions depending on quantity and destination:
| Service | Weight Limit | Cost Per Pound | Delivery Time |
|---|---|---|---|
| Priority Mail | Up to 5 lbs | $1-$3 | 1-3 business days |
| Priority Mail Express | Up to 5 lbs | $1-$3 | 1-2 business days |
| First Class Package | Up to 5 lbs | $1-$3 | 2-5 business days |
| Retail Ground | No weight limit | $1-$3 | 5+ business days |
As you can see above, only 5 pounds or less can be shipped by air. Anything over must use slower ground transportation.
Next let‘s analyze the reasons behind these airline limitations when working with dry ice.
Why Can‘t You Mail Unlimited Dry Ice by Air?
Dry ice undergoes sublimation – transforming from solid to gas – which speeds up at lower air pressures and densities found at high altitudes. This can cause rapid expansion and dangerous pressure buildup.
Most commercial planes fly at over 30,000 feet where lower oxygen concentration and frigid temperatures also accelerate dry ice dissipation.
According to aviation regulators, when confined in a small cargo hold this rapid gas release poses substantial risks:
- Reduced visibility from large amounts of vapor
- Potential oxygen deprivation for crew
- Shortened breathable air supply if depressurization
- Fire or structural damage if pressure limit exceeded
Therefore airlines restrict quantities of dry ice, requiring ground transport for larger volumes exceeding 5 pounds.
Best Practices for Packing Dry Ice Shipments
When preparing dry ice packages, follow these ISTA certified expert recommendations:
Use Proper Insulated Containers
Choose an insulator like hard plastic or polystyrene foam at minimum 2 inches thick to slow sublimation. Line with polyurethane insulating foam for added efficiency.
Allow Venting While Sealing Against Leaks
Seal the container but leave a 1-2 inch opening so gases can escape rather than pressure building up. Absorbent pads also contain excess moisture.
Follow Quantity Guidelines
- 24 hours duration: 4-6 lbs dry ice
- 48 hours duration: 15-20 lbs dry ice
- For medical or sensitive freight, use at least 15 lbs even for 24 hours
Clearly Label and Provide Safety Information
Include required hazardous materials markings per USPS Publication 52 guidelines regarding UN number, net weight, proper shipping name, etc.
By following best practices, you can ensure USPS dry ice shipments arrive intact according to plan. Reach out with any other questions!
