Which type of thermometer should never be used due to contamination risks?

The mercury thermometer is associated with contamination risks mainly due to the toxic nature of mercury. When a mercury thermometer breaks, it can release mercury droplets, which can not only pose a health hazard to individuals exposed to it but also contaminate the surrounding environment. Mercury is a highly toxic substance that can cause serious health effects if inhaled or absorbed through the skin.

In contrast, digital thermometers, infrared thermometers, and bimetallic thermometers do not pose the same level of risk. Digital thermometers typically use sensors to measure temperature without any hazardous materials, while infrared thermometers provide non-contact measurements, eliminating the risk of contamination completely. Bimetallic thermometers use a metal strip that expands with heat to measure temperature and also do not use any toxic substances.

Due to their design, safety concerns, and the potential for environmental contamination, the use of mercury thermometers is discouraged in many settings, such as healthcare facilities and laboratories. This is why the mercury thermometer is identified as one that should never be used due to contamination risks.