These glass thermometers use a non-toxic, non-hazardous liquid and are calibrated and tested against thermometer standards traceable to N.I.S.T. The Enviro-Safe liquid is dyed black for better contast against the yellow bakcing for precise readings. Accuracy is ± one scale division below 105°C (221°F), ± 1.5 scale division above 105°C (221°F), and ± two scale divisions above 200°C (392 °F).