This lecture explores Sick Building Syndrome (SBS), its causes, symptoms, and impact on occupant health and productivity. It examines indoor air quality pollutants such as CO₂, VOCs, formaldehyde, particulate matter, radon, and biological contaminants, along with the role of HVAC systems. The lecture also discusses diagnosis, mitigation, preventive design strategies, low-emission materials, ventilation, moisture control, and continuous IAQ monitoring in intelligent