Category B substances also require triple packaging that includes:
- A primary receptacle
- Secondary packaging
- Rigid outer packaging
An itemized list of contents should be enclosed between the secondary packaging and the outer packaging.
The primary receptacle must be leakproof or siftproof (to prevent leakage if the specimen is dry particulate material) and packaged in such a way that, under normal circumstances, it will not break.
Secondary packaging must also be leakproof or siftproof (such as a sealed plastic bag). For liquids, absorbent material must be placed between the primary receptacle and the secondary packaging, and it must be in sufficient quantity to absorb the entire contents of the primary receptacle to prevent compromising the integrity of the outer packaging if breakage or leakage occurs.
Each primary receptacle(s) must be limited to a volume of 1000 mL (1 L). The package containing category B substances that will be sent by aircraft must be limited to no more than 4L or 4 kg. This excludes ice or dry ice, if either of these are used as refrigerants.
The completed package must be able to survive a drop test of 4 ft.