Yesterday, around 1400 hours, #Truck33 was dispatched for the report of a smoking HVAC unit on Box 07-06. Units went on scene of a 1-story commercial with nothing evident. TK33 arrived as the second truck with six volunteers, positioned on side C, and gave an updated report of smoke from the roof in the rear. Units on the A side forced entry and had smoke showing around the same time. The crew split, immediately sending three men inside and two men to the roof. The inside team accessed the fire building via a series of alleys and assisted with searches and ventilation. The roof team opened up natural vent points and took skylights. The company operated for approximately 45 minutes before returning to service.