Under what condition is a shipper not required to certify that packaging of hazardous materials meets regulations?

The correct choice highlights that a shipper who is a private carrier transporting their own products is not required to certify that the packaging meets regulatory standards. This situation arises because private carriers are handling their own materials and therefore are not acting as commercial entities who transport goods on behalf of others. The regulatory requirements focus more on shippers who are engaged in the commercial transportation of hazardous materials for third parties, which is where the need for certification ensures compliance with safety standards.

In contrast, the other conditions mentioned do not exempt a shipper from this requirement. For instance, if the materials are very small, they still need to comply with regulations regardless of size. Similarly, reused packaging may not necessarily meet safety standards unless it has been properly tested and certified for hazardous material. Finally, transporting hazardous materials for personal use does not relieve the shipper of the responsibility of ensuring that the packaging meets the necessary regulations to prevent hazards during transport.