Introductory technical guidance for mechanical engineers and other professional engineers and construction managers interested in energy efficiency upgrades for air distribution systems in buildings. Here is what is discussed: 1. OVERVIEW OF AIR DISTRIBUTION SYSTEMS, 2. AIR HANDLING SYSTEM TYPES, 3. AIR DISTRIBUTION SYSTEM FANS, 4. FILTERS, 5. INSTALL VARIABLE-SPEED DRIVES, 6. MODIFY CONTROLS, 7. PICK PREMIUM EFFICIENCY MOTORS, 8. USE ENERGY-EFFICIENT BELT DRIVES, 9. CONSIDER A TESTING, ADJUSTING, AND BALANCING CONTRACTOR, 10. SUMMARY, 11. BIBLIOGRAPHY.