Company 1 units were alerted to an Inside Investigation of smoke in a business at 478 Grant Street. Asst. Chief 1 arrived on scene reporting normal conditions from the exterior. Tower 1 crew arrived and made access to the business and an unoccupied space next finding an odor of something burning. The unoccupied space crews found a haze. Engine 1-1 and Engine 1-4 crews arrived and assisted with investigation. Crews found an HVAC unit in the attic space that was malfunctioning and overheating. The overheating was beginning to melt the protective coverings off the duct work. No fire was found and crews removed portions of the flexible ductwork from the attic. Tower 1 crew ventilated the building while crews began to pick up. Command 1(A/C Myers) placed the units in service after operating for about an hour.