This book presents a systematic study on the air balancing technologies in heating, ventilation and air conditioning (HVAC) systems. Several modern air balancing methods, including advanced control-based air balancing, data-driven-based air balancing, and energy-saving-oriented air balancing, are introduced in this book to balance the air duct system. Furthermore, this book provides clear instructions for both HVAC designers and engineers, as well as researchers, on how to design and balance duct systems for improved performance and energy efficiency.