Envirokleen certified thermometers feature black, non-toxic, biodegradable, enviro-safe liquid. black liquid against lead-free, yellow back glass for easy readability and fewer reading errors ideal for use in chemical/petrochemical laboratories, universities, scientific institutions, food and beverage processing, pharmaceutical and medical industries, dairies, breweries and distilleries manufactured and tested by our usa quality team traceable to nist includes multi-language english, french, german, italian, portuguese, and spanish statement of accuracy and traceability, non-roll fitting and individual serial numbershould you require an individual thermometer calibration report, factory calibrated thermometers or custom calibration services are available.