Which of the following statements about labels and placards is true?

The statement that labels and placards are similar in appearance but have different regulations regarding attachment is correct. Labels and placards are both used to communicate hazardous material information, but they serve different purposes and are regulated differently.

Labels are typically smaller and are used on containers to provide information about the hazards associated with the material. They are often affixed to packaging or storage containers and are intended to be visible to those handling the materials. On the other hand, placards are larger and are used on vehicles or at facilities to indicate the presence of hazardous materials. The regulations regarding how and where they must be affixed differ, reflecting their distinct roles in safety and communication.

The other statements do not accurately represent the differences between labels and placards. For instance, labels being exclusive to internal use or being larger than placards is not correct. Additionally, the idea that placards are temporary while labels are permanent does not align with their intended functions. Thus, the correct statement highlights both their similarities in appearance and the differences in regulatory requirements.