Thermco's ASTM - precision factory certified thermometers are calibrated against NlST standards and comes with a calibration document showing corrections to the nearest tenth of a scale division traceable to NIST These thermometers meet with all prescribed ASTM requirements. Each incorporates the ice point when not on scale(0 or 32°F) as a reference point enabling the user to validate and update the calibration document to insure accurate temperature measurements over the life of the thermometers.