A HVAC ventilation system works by circulating air throughout a building or home. It is composed of several components, including a fan, ducts, filters, and dampers. The fan draws in air from outside and pushes it through the ducts, which are connected to the various rooms in the building. The air is then filtered to remove dust and other particles before being pushed into the rooms. The dampers control the amount of air that is allowed to enter each room, allowing for precise temperature control. The system also helps to reduce humidity levels and improve air quality.