This evening around 5PM Cetronia and mutual aid were dispatched to the Friendly's in box 0301 for a report of smoke coming from the air vents. Engine 311 arrived, laid 500' of supply line and stretched an attack line inside to find a haze with a strong odor. Engine 312 arrived and picked up Engine 311's supply line when simultaneously Tower 331 made roof access. Crews traced it back to a faulty HVAC unit and picked up shortly after. Chief 3 (J. Heicklen) had command.