This paper describes a general approach to validating measured data collected for the purpose of evaluating the performance of cool storage systems. The validation approach is a product of ASHRAE Research Project RP-1004,Determining Long-Term Performance of Cool Storage Systems from Short-Term Tests. Ensuring the quality of the data by field validation is preferable to post-processing. However, data validation is necessary to verify the accuracy of measurements, even when sensor accuracy has been verified in the field. Validation is critical if data collected by others are to be used for performance evaluation or if field verification capabilities are limited.The paper presents several tests for verifying the accuracy and consistency of a data set. Tests are based on instantaneous energy balances, energy balances over time, flow balances, and temperature agreements where more than one sensor is measuring the same quantity. The general procedure for the tests is to calculate two or more quantities from selected subsets of the data and verify that they agree within a desired tolerance. Lack of agreement indicates that further analysis or on-site measurements are necessary to determine which sensor(s) are in error.Appropriate tests for a given system generally depend on the specific configuration and operating strategy. This paper describes a number of tests that are applicable to many cool storage systems. The paper also describes two case study sites evaluated for ASHRAE Research Project RP-1004 and illustrates the use of these tests to validate the data from these sites. Recommendations for field monitoring are also provided.The companion paper describes the details of the methodology development and its application to three case study sites (Reddy et al. 2002).Units: I-P