- The internal sensor measures ambient air temperature and the external sensor monitors temperature inside freezers, refrigerators, or cold holding display cases.
- The external sensor has a 3 meter cable and a stainless steel, blunt probe enclosed in a sealed plastic bottle of propylene glycol, a solution that is classified as GRAS (generally recognized as safe).
- This enclosure prevents false alarms because the measurements of the probe are not impacted by rapid temperature fluctuations caused by frequent door openings that occur during normal use.
- This thermometer mimics temperature readings in a medium similar to the common fluids stored in refrigerators and freezers in pharmacies and labs.
Exposure to heat and cold can damage vaccines reducing potency and according to the CDC Vaccine Storage & Handling Toolkit just one exposure to freezing temperatures can destroy some refrigerated vaccines. This is why monitoring vaccines throughout the cold chain is vitally important and why the CDC recommends the use of calibrated thermometers for use in tracking vaccine temperatures. They further recommend the use of probes suspended in glycol to provide a more accurate reading of liquid temperatures.