Company's 3, 31 and the Rescue Squad responded to the FSK Mall for a report of smoke in the building. Medic 319 arrived on scene first to find normal conditions from the exterior. After interviewing the occupants they confirmed there was an odor in the FMH Wellness center. Duty 3 arrived and established the command as Engine 31 arrived 1st and dropped a line from the hydrant to the building. Medic Engine 311 arrived along with Truck 41 and secured the water supply as crews entered the building to investigate. The truck laddered the roof and found a faulty HVAC unit. The unit was secured and the building was ventilated. Units returned to service a short time later.