The U.S. Department of Transportation’s (DOT) Federal Aviation Administration (FAA) issued Safety Alert for Operators (SAFO) No.10017 on October 10, 2010. The subject of this SAFO pertains to the “Risks in Transporting Lithium Batteries in Cargo by Aircraft” and is intended to alert operators to the recent findings from the FAA William Hughes Technical Center test results on the particular propagation characteristics that are associated with lithium batteries. FAA tests follow the United Parcel Service (UPS) Flight 006 crash in the United Arab Emirates on September 3, 2010. Although investigation of the crash is still underway, and the cause of the crash has not been determined, investigators are aware that the plane’s cargo did include large quantities of lithium batteries. In coordination with the FAA, the Pipeline and Hazardous Materials Safety Administration (PHMSA) is considering the best course of action to address the risk posed by lithium batteries. In the interim, SAFO 10017 includes recommended action that carriers should consider adopting when transporting lithium batteries.
FAA tests have demonstrated how lithium ion cells are flammable and capable of self-ignition that occurs when a battery short circuits, is overcharged, is heated to extreme temperatures, is mishandled, or is defective. Lithium ion batteries, like lithium metal batteries, can be subject to thermal runaway. Thermal runaway is a chain reaction that occurs when sufficient heat is generated to cause adjacent cells to go into thermal runaway. A battery in thermal runaway can reach temperatures above 593°C (>1,100°F), which exceeds the ignition temperature of most Class A materials, including paper and cardboard. These temperatures are also very close to the melting point of aluminum; 660°C (1,220°F). Though the result of thermal runaway in a lithium metal cell is a more severe event than a lithium ion cell in thermal runaway. The lithium metal cell releases a flammable electrolyte mixed with molten lithium metal, results in an explosive mixture.
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 (the suppression agent found in Class C cargo compartments), 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.
To demonstrate the safety risk that encased or enclosed lithium metal batteries may pose, 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. Commonly available metal shipping containers, pails and drums, are not designed to withstand a lithium metal cell fire. There are currently no approved and tested containers that can sufficiently contain the known effects of accidental lithium metal battery ignition.
Until then, the FAA recommends that all air carriers institute the following additional procedures for safely transporting lithium batteries by aircraft:
- Request customers to identify bulk shipments of currently excepted lithium batteries by information on airway bills and other documents provided by shippers offering shipments of lithium batteries.
- Where feasible and appropriate, stow bulk shipments of lithium batteries in Class C cargo compartments or in locations where alternative fire suppression is available.
- Evaluate the training, stowage, and communication protocols in your operation with respect to the transportation of lithium batteries in the event of an unrelated fire.
- Pay special attention to ensuring careful handling and compliance with existing regulations covering the air transportation of Class 9 hazardous materials, including lithium batteries.
These recommendations are limited to lithium batteries transported in the cargo hold of an aircraft (including cargo holds that are not distinct from the flight deck), and do not apply to lithium batteries carried onboard by passengers and crewmembers, or otherwise stowed in the passenger cabin of the aircraft. Also, these recommendations are not exclusive. The FAA hopes that carriers will use the information provided in SAFO 10017 and in their Tech Center study, together with any other available information, to consider other reasonable measures they believe appropriate to mitigate the risk of transporting lithium batteries by air.