What Are the Key Packaging Requirements for UN3373 Substances Under PI 650?

Do you ship UN3373?

If your organization ships UN3373 Biological Substance, Category B materials in the United States, understanding the legal packaging requirements is essential. Below is a summary guide to the key requirements under Packing Instruction PI 650 and CFR173.199.

For companies looking to purchase UN3373 compliant packaging or a complete UN3373 shipping kit USA, this guide outlines what is legally required.

Unlike packaging for Category A Infectious Substances, packaging for Category B does not have to be UN approved, however, it does need to have demonstrated that it can pass certain performance tests.

Under PI 650 or CFR 173.199, the packaging must consist of three components:

1. Primary receptacle (leakproof for liquids or siftproof for solids)
2. Secondary packaging (leakproof for liquids or siftproof for solids)
3. Rigid outer packaging

This structure forms a compliant UN3373 triple packaging system.

Primary Receptacles: Key Requirements

Primary receptacles must be:

• Leakproof for liquids
• Siftproof for solids

They must be packed so that, under normal transport conditions, they cannot break or leak into the secondary packaging.

When multiple fragile primary receptacles are placed in one secondary package:

• Each receptacle must be individually wrapped or separated to prevent contact
• If liquids are present, sufficient absorbent material must be placed inside the secondary packaging
• The absorbent material must be capable of absorbing the entire contents of the primary receptacles

Secondary Packaging: Key Requirements

Secondary packaging must be:

• Leakproof for liquids
• Siftproof for solids
• Primary or secondary packaging must be 95 kPa capable for liquids shipped under P650

Common examples include 95kPa biohazard bags or 95kPa specimen transport bags used as compliant secondary packaging.

95 kPa Requirement

For liquid substances, either the primary receptacle or the secondary packaging must withstand an internal pressure of 95 kPa (0.95 bar) without leakage.

This requirement is particularly important for air transport and is a critical component of IATA P650 compliant packaging.

Businesses looking to buy 95kPa biohazard bags should ensure the bags have been independently tested to meet this pressure requirement.

Outer Packaging Requirements

The outer packaging must:

• Be rigid
• Have a minimum dimension of 100 mm × 100 mm (3.9 in × 3.9 in) on at least one surface
• Include an itemized list of contents placed between the secondary and outer packaging
• Successfully withstand a 1.2 meter drop test without leakage

Marking Requirements

The package must display:

• The UN3373 mark, set at a 45-degree angle (diamond-shaped), with a minimum side length of 50 mm
• The text “BIOLOGICAL SUBSTANCE, CATEGORY B” in letters at least 6 mm high

Dry Ice

If Dry Ice is used, it must be placed:

• Outside the secondary packaging
• In the outer packaging
• Or within an overpack

These requirements apply whether shipping domestically within the U.S. or internationally.

Summary: What Is Required to Ship UN3373 Legally?

To legally ship UN3373 substances, you must use a UN3373 compliant triple packaging system that includes:

• Leakproof or siftproof primary and secondary containers
• One layer (primary or secondary) capable of withstanding 95 kPa pressure for liquids shipped via P650
• Sufficient cushioning and absorbent material (for liquids)
• Outer packaging capable of passing a 1.2 meter drop test
• Proper UN3373 diamond marking and Category B identification text

Failure to meet any of these requirements can result in rejected shipments and regulatory non-compliance.

Looking for UN3373 Compliant Packaging in the USA?

If your laboratory, hospital, diagnostic facility, or biotech company needs UN3373 compliant packaging, we offer:

• 95kPa specimen transport bags
• 95kPa biohazard bags tested to PI 650 requirements
• Complete UN3373 shipping kit USA solutions
• Bulk UN3373 packaging kits for high-volume operations
• Temperature control packaging for temperature regulated UN 3373 shipments

Whether you need to order individual 95kPa biohazard bags or purchase a complete Category B shipping kit, our solutions are designed to meet PI 650 and CFR 173.199 requirements.

Learn More About UN3373 & 95kPa Packaging Requirements

We provide educational resources to help businesses understand infectious substance shipping regulations, including:

• Detailed guides on UN3373, UN2814, and UN2900 packaging requirements
• Information explaining what 95 kPa bags are and why they are required
• Demonstration videos of 95 kPa pressure testing

For more information about our UN3373 compliant packaging solutions, or to request pricing on 95kPa biohazard bags and UN3373 shipping kits, contact our team today.

Information correct at time of publication. Published Date 20 Feb 2026