Your best source for complete information on the NFPA 70E Standard is via the actual standard, available for purchase at www.nfpa.org. In 2000, the NFPA 70E Standard first addressed electric arc flash hazard and required flame resistant arc flash clothing to protect workers. The current edition of the NFPA 70E standard was released in 2012, and further details personal protective equipment.
Fluoride ions exist predominantly as hydrofluoric acid in acidic environments with a pH below 5.2. Fluoride ions corrode the glass. Therefore, the pH measurement with the glass electrode for a solution which includes fluoride ions is basically impossible. Although the useful life of the electrode may be shortened, however, the measurement with immersing the electrode in the sample for a given short time is possible.
Examples include sodium fluoride, stannous fluoride, and fluoride monofluorophosphate (MFP fluoride). Some fluorides occur naturally in soil, air, or water, although the levels of fluoride can vary widely. Just about all water has some fluoride. Fluoride is also found in plant and animal food sources.luoride is now used in the public drinking water supplied to about 3 out of 4 Americans. The decision to add fluoride to drinking water is made at the state or local level. The types of fluoride added to different water systems include fluorosilicic acid, sodium fluorosilicate, and sodium fluoride.