A VAV box, or Variable Air Volume box, is a type of air handling unit used in HVAC systems. It is designed to control the temperature and air flow in a building or space. The VAV box is typically connected to a duct system, which distributes the air throughout the building. The VAV box is designed to adjust the air flow based on the temperature in the space, allowing for more efficient energy use. It also helps to maintain a comfortable temperature in the space, as the air flow can be adjusted to match the needs of the occupants. The VAV box is a key component of any HVAC system, and is essential for maintaining a comfortable environment in a building or space.