PackSafe - Thermometers
Medical-Clinical Mercury Thermometer
Small medical thermometer
Quantity limits: One small medical or clinical mercury thermometer for personal use, when carried in a protective case in checked baggage.
The thermometer must be in a protective case.
Regulation that allows it: 49 CFR 175.10(a)(7)
Tip: thermometers with a red line instead of silver are not mercury and not restricted. Digital thermometers are also not restricted.
Mercury Barometer or Thermometer
Carried by government weather bureau or similar official agency.
These devices contain more mercury than consumer devices (see separate entry in this table for medical/clinical thermometers) and may only be carried by a representative of a government weather bureau or similar agency.
Must be in carry-on baggage only.
The individual must advise the airline of the presence of the mercury barometer or thermometer in the carry-on baggage.
Must be inside a strong outer packaging having a sealed inner liner or bag constructed of strong, leak-proof and puncture-resistant material that is impervious to mercury and will prevent the escape of mercury from the package in any position.
See the regulation: 49 CFR 175.10(a)(13)