Frederick County Emergency Communications received the initial call from CSX representatives at 7:51 a.m. reporting a tanker leaking a refrigerant product called ethylene, a flammable liquid used in industrial processes. The leaking tanker was believed to hold 137,000 pounds of the product.
"It's minus 300 degrees when it comes out. It looks like a frost. We got the valve sealed off", Assistant Chief Houser said about 5:30 p.m. Saturday as crews stopped for a break. The valve appeared to have been worn down by age.
About 75 people representing law enforcement and fire rescue services descended on the southern scene to deal with the incident.
One career firefighter from the county's Department of Fire Rescue Services was treated for heat exhaustion at Frederick Memorial Hospital, but there were no other injuries, officials said.
HAZMAT teams from Fort Detrick and Loudoun County, Va., responded, as well as the National Park Service from Harpers Ferry, WV, and a Montgomery County, MD, ambulance crew.
Deputies with the Frederick County Sheriff's Office assisted Brunswick police officers with traffic control and containing the scene.