October 10, 2010 - The Department of Transportation’s Federal Aviation Administration (FAA) on Friday alerted operators to results of new research on the risks associated with transporting lithium batteries as cargo on aircraft and recommended actions air carriers can take to reduce those risks.

In a Safety Alert for Operators (SAFO), the FAA summarized recent research which shows that lithium metal (non-rechargeable) and lithium-ion (rechargeable) batteries are highly flammable and capable of igniting during air transport under certain circumstances.

The research also indicates that Halon 1301, the suppression agent found in Class C cargo compartments, is ineffective in suppressing lithium metal battery fires.

United Parcel Service Flight 006 crashed in the United Arab Emirates on September 3, 2010. Investigation of the crash is still underway, and the cause of the crash has not been determined. The FAA is aware, however, that the plane’s cargo did include large quantities of lithium batteries.

Lithium metal batteries are highly flammable and capable of ignition. Ignition of lithium metal batteries can be caused when a battery short circuits, is overcharged, is heated to extreme temperatures, is mishandled, or is otherwise defective. Once a cell is induced into thermal runaway, either by internal failure or by external means such as heating or physical damage, it generates sufficient heat to cause adjacent cells to go into thermal runaway.

The result of thermal runaway in a lithium metal cell is a more severe event as compared to a lithium-ion cell in thermal runaway. The lithium metal cell releases a flammable electrolyte mixed with molten lithium metal, accompanied by a large pressure pulse. The combination of flammable electrolyte and the molten lithium metal can result in an explosive mixture. Halon 1301, the suppression agent found in Class C cargo compartments, is ineffective in controlling a lithium metal cell fire.

The explosive potential of lithium metal cells can easily damage (and potentially perforate) cargo liners, or activate the pressure relief panels in a cargo compartment. Either of these circumstances can potentially lead to a loss of Halon 1301, allowing rapid fire spread within a cargo compartment to other flammable materials. For this reason, lithium metal cells are currently prohibited as bulk cargo shipments on passenger carrying aircraft.

FAA testing has shown that encased or enclosed lithium metal batteries may pose a safety risk. Two types of robust, readily available containers were tested at the FAA Tech Center: five gallon steel pails with crimp on gasketed lids, and 30 gallon steel drums with bolt closed ring seals and gasketed metal lids.

For both types of container, as few as six loose CR2 lithium metal cells were sufficient to cause failure when induced into thermal runaway by an electric cartridge heater. The confined electrolyte and the molten lithium ignition source formed an explosive condition, forcefully separating the lid from the container. The explosive force in this test was likely high enough to cause physical damage to an aircraft’s Class C cargo compartment.

A container specially designed to ship lithium metal batteries would need to demonstrate that it can withstand this explosive condition. There are currently no approved and tested containers that can sufficiently contain the known effects of accidental lithium metal battery ignition. Common metal shipping containers, pails and drums, are not designed to withstand a lithium metal cell fire.

FAA test results have also demonstrated that lithium-ion cells are flammable and capable of self-ignition. Self-ignition of lithium-ion batteries can occur when a battery short circuits, is overcharged, is heated to extreme temperatures, is mishandled, or is otherwise defective. Like lithium metal batteries, lithium-ion batteries can be subject to thermal runaway. A battery in thermal runaway can reach temperatures above 1,100 degrees F, which exceeds the ignition temperature of most Class A materials, including paper and cardboard.