At 09:43 on April 1st, while returning to quarters from a motor vehicle accident, Engine 311 was alerted for the report of a building fire in the 1700 block of Reisterstown Road. E-311 arrived on scene first and established command, with smoke in the interior. Upon arrival of Truck 18, crews went to the roof to investigate the source of the smoke. Crews quickly identified an overheating air handling unit and shut it off. Crews ventilated the establishment and returned to service after operating for 25 minutes.