At approximately 1900hrs Engine 22 and Tanker 2 responded mutual aid to St. Mary's County, Co. 2's area, for the working house fire. Engine 22 picked up SM E-24's LDH line and the crew assisted MVFD personnel with extinguishment of the fire. The fire was brought under control and extinguished very quickly but, due to the extensive overhaul operations crews remained on the scene for approx 3hrs. HVFD units cleared the scene around 2200hrs.