This standard prescribes the methods for testing the performance of air-to-air heat/energy exchangers. In this standard@ an air-to-air heat/energy exchanger is a device to transfer heat and/or water vapor from one airstream to another. The types of air-to-air heat/energy exchangers covered by this standard are a. regenerative energy exchangers (including heat wheels and total energy wheels)@ b. heat pipe exchangers@ c. thermosiphon exchangers@ d. recovery loop exchangers (also called run-around exchangers)@ and e. fixed-plate exchangers. The scope of this standard also includes both laboratory and field tests@ provided that appropriate levels of uncertainty can be achieved when testing. A test is deemed to be within the scope of this standard if both a pretest uncertainty analysis and a posttest uncertainty analysis yield satisfactory uncertainty limits. PURPOSE The purpose of this standard is to a. establish a uniform method of test for obtaining performance data for air-to-air heat/energy exchangers; b. specify the test conditions@ data required@ uncertainty analysis to be performed@ calculations to be used@ and reporting procedures for testing the performance of an air-to-air heat/energy exchanger; and c. specify the types of test equipment for performing such tests