By Bill Carey
BALTIMORE — The Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) Baltimore Field Division released a technical report and video from its investigation into the line-of-duty death of Howard County, Maryland, Firefighter Nathan Flynn on July 23, 2018.
ATF personnel used engineering analysis methods, including field fire testing, large-scale laboratory fire testing, advanced computer fire modeling and electronic data sources, to help identify the origin and cause of the fire, the route of fire spread throughout the structure, and the events that led to Flynn’s mayday and death.
The report indicated that the fire involved corrugated stainless-steel tubing (CSST) that ran through the crawl space beneath the living room. A lightning strike energized the propane distribution system, causing the CSST in the crawl space to arc to a nearby grounded object. This resulted in a small hole forming in the CSST gas line, which allowed propane gas to leak from the hole and also likely ignited the escaping gas at the same time.
Residents called 911 approximately 30 minutes after the lightning strike when they noticed smoke in their living room. One hour after the lightning strike, Firefighter Flynn called a mayday after he fell through the living room floor into the burning crawl space below. A similar sequence of events resulted in the death of Captain Joshua Laird in Ijamsville, Maryland, three years later. ATF also provided technical assistance at that Ijamsville LODD fire scene and concluded that lightning-induced failure of CSST resulted in a basement fire, floor collapse and the subsequent death of Captain Laird.
The report emphasizes that no single root cause event led to Firefighter Flynn’s death. Five conclusions were developed from the fire development analysis:
An extremely large volume of the residence allowed for a well-developed fire, despite light smoke showing on the exterior;
An elevated fire located in the basement crawl space created atypical smoke-filling conditions in the basement;
A ventilation flow path existed from the basement door (inlet), through the hole in the crawl space and out the first-floor mud room door (outlet). This flow path created untenable conditions on the first floor during the mayday;
When a lightning strike is suspected, ceiling space in the basement should be opened up to rule out a concealed fire due to multiple parallel CSST lines routed through interstitial spaces; and
The similar findings from this LODD and an earlier one also caused by lightning-induced failure of CSST in the basement point to multiple fact-based similarities and highlight the importance of the conclusions in this report.