This International Standard specifies a method for the measurement of trace amounts of basic materials present in polyether polyols used in the production of polyurethanes. It is important to know the trace amount of basicity in a polyol to prevent gelation of the reaction mass during the production of polyurethane prepolymers. It is also useful to control the basicity in polyols used for polyurethane production to assure consistent and reproducible reaction behaviour. This method is suitable for quality control, as a specification test and for research. The applicable range is 0 μg to 50 μg/g, expressed as KOH. The method is not applicable to amine-based polyols. The values may be reported as CPR (controlled polymerization rate) units.