This book offers a comprehensive overview of the principles, design, installation, and maintenance of air conditioning and ventilation systems. It covers a wide range of topics, including psychrometrics, load calculations, equipment selection, ductwork design, air distribution, energy efficiency, indoor air quality, and system control. Additionally, it addresses emerging trends and technologies, such as smart HVAC systems and sustainable ventilation solutions. By examining various aspects of HVAC systems—crucial components of building mechanical systems—the book highlights their role in ensuring thermal comfort and maintaining indoor air quality, thus enhancing the overall functionality and livability of buildings.