Can passengers carry a small mercury thermometer for personal use when appropriately protected?

The ability for passengers to carry a small mercury thermometer for personal use when appropriately protected is acceptable according to regulations that prioritize safety and precaution. Mercury thermometers are considered hazardous materials because of the toxic nature of the mercury they contain; however, when properly packaged to prevent breakage and leakage, they can be transported.

The understanding of "appropriately protected" plays a crucial role here. If a thermometer is in a sturdy case or wrapped securely to prevent accidental shattering, it minimizes the risk of mercury exposure, aligning with safety protocols.

The other answer choices suggest limitations or outright bans that do not recognize this context of safe transport. Dismissing the ability to carry the thermometer based on its purpose or suggesting it must be disposable overlooks the fact that personal use is permitted when safety precautions are taken. Therefore, the correct choice highlights the balance between safety and the practical need for some items, like thermometers, in personal care.