4-01 Box, 22:43 - Ridge units responded to Mill Field Drive in St. Mary's City for the reported commercial building fire. Chief 4B arrived on location at 22:51 and reported that there was a slight odor of smoke in the building and established the command. Engine 141 arrived shortly after and started the investigation on division 1 (First Floor). Engine 43 arrived and reported to subdivision 1 (Basement / Mechanical Room). After further investigation it was determined that a boiler pump overheated and discharged smoke through the building. Personnel naturally ventilated the space of origin. Units cleared at 23:43.