This standard covers a practice for the determination of hydroxyl numbers of polyols using NIR spectroscopy. Definitions, terms, and calibration techniques are described. Procedures for selecting samples, and collecting and treating data for developing NIR calibrations are outlined. Criteria for building, evaluating, and validating the NIR calibration model are also described. Finally, the procedure for sample handling, data gathering and evaluation are described. The implementation of this standard requires that the NIR spectrometer has been installed in compliance with the manufacturer's specifications. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Note 1 -There is no equivalent or similar ISO standard.