What happened
During the flight, a passenger was wearing an Ecoquest Fresh and Air Buddy Personal Air Purifier around his neck. The passenger was also observed using a Sprint Trio 700 camera phone near a window. While holding the telephone to the window, a noise similar to a fuse was heard, followed by a flash, a loud bang, and smoke emanating from the air purifier device.
The passenger removed the device after it began to burn him. The air purifier then exploded into a ball of flames approximately the size of a volleyball and fell between the seat cushions, initiating a fire. Passengers attempted to extinguish the smoldering cushions using water and other liquids, while a flight attendant utilized a Halon fire extinguisher to suppress the flames. The battery from the device was not recovered.
The investigation
An NTSB fire and explosion expert examined the air purifier. The investigation found that while the device originally included a 3.6V CR123A non-rechargeable lithium primary battery, a separate kit containing a charger and a rechargeable lithium-ion battery was available for purchase.
The examination of the device revealed that the battery compartment cover was melted and deformed, featuring two areas of metal splatter. Analysis of this splatter identified the presence of manganese. Because manganese dioxide is a component in primary, non-rechargeable lithium batteries, this finding was significant to the analysis of the failure.