Mercury is a neurotoxin and can also damage the lungs and kidneys when mercury vapors are inhaled. However, as the only metal that is liquid at room temperature, mercury expands and contracts evenly with temperature and pressure changes. These characteristics make mercury useful in providing very accurate and precise measurements for temperature, pressure, and more. For these reasons, UMass does not prohibit their use, though you should only use mercury-containing devices if no viable alternatives can be found. Please follow the recommendations in the fact sheet linked above information about safe handling and disposal of devices.