Incident Overview
During the climbout phase from the departure airport, a flight attendant observed smoke emanating from an overhead bin containing a bag of camera equipment. The flight attendant extinguished the smoke and immediately informed the captain. The captain declared an emergency, and the aircraft returned to the departure airport, landing without further incident approximately 6 minutes later.
Examination of Equipment
Subsequent examination of the camera equipment bag revealed that the remnants of a 9-volt battery had sustained damage consistent with a catastrophic battery failure. The main component of the 9-volt battery had a flashpoint of 21 degrees Fahrenheit, equivalent to room temperature. Within the same pocket of the equipment bag, other batteries were found with unprotected contacts, including two fully charged 14-volt battery packs. One of these 14-volt battery packs displayed significant exterior thermal damage, consistent with damage from contact with another battery.
Battery Fire Research
Battery industry research indicates that short circuits are the most common cause of battery fires, often initiated when battery contacts come into contact with metal objects. Batteries are generally not designed to contain catastrophic failures; when they enter thermal runaway, they can explode and expel contents into the environment, potentially igniting materials well beyond the initiating battery cell.