We have a liquid in glass thermometer that has not been calibrated since 2010, but we have been using NIST-traceable thermometers on a daily basis and checking them each day using an ice bath. My question is, do we need to have the liquid in glass if we are using NIST-traceable thermometers to take temperatures? It seems very redundant. It seems that we originally got the liquid in glass thermometer for USDA. Does anyone know what other methods of verifying the calibration on thermometers used in production?