Selection of air-to-air heat-recovery systems for application in research laboratory air systems requires a thorough analysis of available equipment and economic factors associated with installation and operational expenses. A comprehensive engineering investigation of the air-handling systems in two buildings in research laboratories at Rochester, New York, resulted in the installation of "thermosiphon (heat pipe)" and "run-around coil" air-to-air heat-recovery systems. "Rotary wheel" and "fixed plate" heat-recovery systems were considered and rejected for these applications. This paper will review for these specific applications the (1) assets and liabilities of the four systems considered, (2) selection process, (3) installation and operational economics involved, and (4) obtained operation experience.