Engine/Tanker 24 and Baltimore County Battalion Chief 22 arrived simultaneously at a reported garage fire involving exposures on Marshall Mill Road in Baltimore County. Beginning at the end of the driveway, 600 feet of the 5-inch supply line was laid out as ET-24 proceeded up the long driveway to the fire scene. At the top of the driveway, ET-24 and BC-22 encountered heavy fire and smoke from a fully involved single story garage. Two 1-3/4 inch attack lines were deployed. The first hose line was used to protect (cool) the nearby home where the vinyl siding had begun melting from the intense heat of the fire. The second hose was used to attack the seat of the fire. BC-22 and ET-24 rescued two dogs that were in an enclosure attached to the burning garage. With the initial cooling of the exposed side of the home complete, focus shifted to cooling a recently filled, 250 gallon propane tank next to the garage that had started venting from the pressure relief valve. The venting gas ignited a short time later. The bulk of the main fire in the garage was knocked down, and only the propane from the venting tank continued to burn. For about 2.5 hours, a constant stream of water was used to cool the tank while the propane was allowed to burn off. Carroll County Engine/Tanker 44 arrived and provided manpower and water. Upon arrival, Carroll County Tanker 7 was used as a nurse tanker. As more units arrived, all first alarm units were utilized in the water supply operations until a water supply operation could be established. Not being needed, Truck 2 returned to the station and the crew brought Engine 23 to the water supply fill site (hydrant) in the Hampstead Village Shopping Center to assist with filling the tankers. Baltimore County Police Department Fire Investigation Division is investigating the cause of the fire.