The specifications regarding temperature measuring devices can be found in the “Manual for the Certification of Laboratories Analyzing Drinking Water, Criteria and Procedures Quality Assurance, 5th ed.”, USEPA, Document ID 815-R-05-004 (January 2005). If the laboratory is running drinking water compliance samples, it is recommend they download a copy of this manual as additional reference. They can google “USEPA drinking water laboratory certification manual” or go directly to it through the following link:
Within the manual, in Chapter IV, Sect. 7.1.5 (Temperature Measuring Devices), it states: “Liquid bearing thermometers such as mercury or alcohol thermometers need to be traceable to NIST calibration and verified at least annually and whenever the thermometer has been exposed to temperature extremes.....The NIST thermometer should be recalibrated at least every five years or whenever the thermometer has been exposed to temperature extremes.” There is additional information in the manual regarding digital thermometers, thermocouples, and infrared thermometers.