Evaluation of the accuracy of lower-flammability-limit sensors with the use of field-portable extractive fourier-transform infrared spectroscopy

Lower-flammability-limit (LFL) sensors have recently been installed in the drying ovens and web tunnel of a commercial tape manufacturing process line. Calibration of the LFL sensors by the sensor manufacturer was accomplished by creating a cocktail of solvents that was similar in composition to tape formulations that are used at the manufacturing plant, and then exposing a calibration LFL sensor to various amounts of the cocktail. A calibration curve was generated from the response of this sensor to various concentrations of the cocktail, and then it was exported to all of the process LFL sensors. To verify the accuracy of the process LFL sensors, extractive Fourier-transform infrared (FTIR) spectroscopy was used to measure the concentrations of solvents present at the LFL sensor probe locations while the LFL sensor readouts were read and recorded. The extractive FTIR solvent concentration measurements were converted to % LFL and compared to the readings generated by the LFL sensors. © 2000 John Wiley & Sons, Inc. Field Analyt Chem Technol 4: 62–69, 2000