This standard prescribes methods for testing the performance of certain air-to-air heat exchangers.In this standard@ an air-to-air heat exchanger is a device utilized to transfer heat from one airstream to another. The types of air-to-air heat exchangers covered by this standard are(a) rotary energy recovery wheels(b) heat pipe exchanger(c) thermosiphon exchanger(d) coil recovery loop exchanger(e) fixed plate exchanger(f) open spray recovery loop exchangerThis standard is not intended for testing a packaged system@ sometimes called a heat recovery ventilator.