Boston, Massachusetts: Lithium-Ion Batteries Caused the Dorchester Fire That Killed Firefighter Bobby Kilduff

Boston fire officials said on Wednesday that lithium-ion batteries stored in plastic toolboxes on an enclosed porch caused the fire that killed Boston firefighter Robert "Bobby" Kilduff Jr. in Dorchester in May.

Fire Commissioner Rodney Marshall announced the cause at a Wednesday press conference with Mayor Michelle Wu, WCVB reported. Investigators found that multiple lithium-ion batteries sparked the three-alarm fire at 18 Treadway Road on May 23, according to the Boston Globe. Marshall said the batteries went through thermal runaway, a process in which battery cells overheat and set off a chain reaction.

Kilduff, 53, was a 24-year veteran of the Boston Fire Department and a member of Rescue Company 2. He was a third-generation firefighter. He died after falling from the third floor of the house while battling the blaze on May 23.

The cause is settled, the death inquiry is not

Wednesday's announcement closes the question of what started the Treadway Road fire. It does not close the question of how Kilduff died. Two investigations into the circumstances of his death are still running: one by the National Institute for Occupational Safety and Health, and one by a Boston Fire Department Board of Inquiry. Officials said the findings of both reviews will be shared with the public when they are complete.

The Boston Fire Department has seen an increase in fires caused by lithium-ion batteries in recent years, MassLive reported, and residents often keep as many as a dozen of the batteries in their homes. The batteries power e-bikes, scooters, tools and other everyday devices, and fire officials used Wednesday's announcement to press the department's long-running warning about how they are charged and stored.

City Council takes up battery safety

Boston City Councilor Ed Flynn has filed a hearing order on lithium-ion battery safety, focused on the batteries used in electric bikes, scooters and other micromobility devices. No hearing date has been announced.

The Treadway Road fire is the deadliest test so far of a problem Boston firefighters say they now meet in homes across the city: batteries stored in bulk, in plastic containers, on a porch, close to an exit route. With the cause now on the record, the two open investigations will decide what the department changes next.

Rescue Company 2 is one of the Boston Fire Department's heavy rescue companies, and its crews answer major incidents across their side of the city. Kilduff's death was a line of duty death, the kind the federal NIOSH process exists to examine, and his company has carried the May fire with it into every shift since.