Smartavia Answer Center

A medical thermometer containing mercury may be carried both in checked baggage and in hand luggage, provided it is packed in a sturdy outer packaging set containing a sealed inner liner or bag made of a strong, leak-proof or puncture-resistant material that does not allow mercury to pass through, and which prevents the leakage of mercury from the package regardless of its position.

In other words, a mercury thermometer must be packed securely so that it does not break, and so that, if the thermometer does break, the packaging prevents mercury from escaping beyond it.

A thermometer that does not contain mercury may also be carried both in checked baggage and in hand luggage.