Calcium Fluoride (CaF2) has long been used in research applications. It performs best in controlled environments where humidity, chemical exposure, vibration and high frequency noise are minimized or eliminated. The transmission rate characteristics of CaF2 are suitable for higher temperature applications, shortwave and midwave thermography and for the visual spectrum. Medium to longwave transmission rates (7-14 micron) are typically between 40-50% based on the infrared (IR) camera detector sensitivities at different wavelengths. VPFC Series (Viewing Pane Fixed Crystal) IR windows are specially coated to reduce the transmission drift due to moisture/humidity. However, industrial users are strongly encouraged to investigate the VPT Series of industrial-grade IR windows which are specifically designed for stability in harsh industrial environments and have an unconditional lifetime warranty. When purchasing crystal windows, ask for the Material Safety Data Sheet (MSDS) to ensure that the crystal does not contain hazardous substances. Some window manufacturers use crystals made of Barium Flouride (BaF2), a toxic substance, especially hazardous to the food and beverage industry.