Hazard : FAA Cargo Fire Safety

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Hazard: Lithium Metal Batteries Shipped In Or With Equipment UN 3091

Lithium-metal batteries shipped with equipment have a similar hazard as lithium-metal cells and batteries shipped in bulk except the equipment may provide some buffer zone between adjacent batteries and adjacent packages and reduce the likelihood of propagation.

However, unlike batteries shipped on their own. Electronic equipment has a possibility of activating during transportation and causing a heat source for thermal runaway to occur.

A single cell (AA, AAA, C, 18650, cr123, etc., usually referred to as a battery by consumers) may be defined as a single encased electrochemical component and a battery (power drill battery, power pack, drone battery, etc.) is two or more cells electrically connected. Non-rechargeable lithium-metal cells and batteries are manufactured in various shapes, sizes, and chemistries depending on the application. The image below: Variety of Lithium-Metal Cells shows examples of cells that may be installed in equipment and packaged according to UN 3491.

Lithium-metal cells and batteries are capable of overheating and undergoing a process called thermal runaway. Thermal runaway can occur without warning as a result of various factors, including if the package is damaged, overheated or improperly packed. Thermal runaway can also occur on its own due to manufacturing defects, without any environmental or mishandling factors. See video: Battery Thermal Runaway

The outcome of thermal runaway varies depending on the specific chemistry of lithium-metal, the size of the cell or battery, whether it’s fully charged, the individual manufacturer design as well as orientation and configuration in the package. The more dangerous hazards can include violent ejection of flames and battery components, emission of flammable gas that can build up and later explode or an explosion of the cell itself. Less hazardous outcomes include an emission and dissipation of flammable vapors without ignition or accumulation of gas or a thermal runaway event that catches fire but self-extinguishes. See videos: Flammable Gas Buildup and Explosion and Explosion of Cell Itself. Research on flammable gasses released: Flammable Gases

An important factor related to the hazard of thermal runaway is an event called “thermal runaway propagation”. Propagation occurs when the heat from one battery or cell causes an adjacent battery or cell to also undergo thermal runaway. This can repeat itself over and over until an entire pallet of batteries has undergone thermal runaway creating enormous amounts of heat, smoke, and flammable gases. For this reason, mitigation techniques can be employed to prevent propagation if thermal runaway of a single cell does occur. See video: Large Scale Thermal Runaway Propagation

The transportation regulations establish the minimum requirements for the shipment of non-rechargeable lithium-metal cells or battery packages shipped with equipment. These minimum packaging regulations/standards can be found in title 49 CFR 173.185 or the ICAO Technical Instructions for the Safe Transport of Dangerous Goods Part 4 Packing Instructions 969 and Packing Instruction 970.

UN 3091 can encompass a variety of different types and configurations of lithium-metal cells and batteries with equipment, making it difficult to assess the hazard associated with the package simply by looking at the label alone. For example, a shipment of cells or batteries posing a significant thermal runaway hazard may use the same packaging and labeling as a shipment containing comparatively safe and benign lithium-metal cells and batteries. It is important to keep this in mind when creating a safety management plan for the transportation of lithium-metal cells and batteries.

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