Two characteristics of lithium batteries explain how passengers and cargo must be protected from harm during commercial air transport flights. Cells within all lithium batteries are capable of self-ignition and entering a thermal runaway state. Moreover, recent trends in aircraft incident data show that technological advancements and new uses of lithium batteries require continual attention. Aviation professionals, passengers and other stakeholders must periodically update their knowledge and skills to effectively mitigate this risk. This article supplements Aircraft Fire Risk from Battery-powered Items Carried on Aircraft to increase awareness of the following cabin-safety issues. Beginning around 2015, these issues emerged separately and led to new or revised international rules and guidance on best practices:
- Smart luggage (also called smart bags);
- Spare lithium batteries;
- Power banks;
- Electronic baggage tags;
- Electric scooters; and,
As with previous generations of lithium batteries, PEDs and entirely new categories of devices, education and training on any unfamiliar subject become essential for stakeholders directly engaged in flight operations — especially aircraft crewmembers — and recommended for those who have indirect responsibilities. The scope of such new information includes current rules of carriage; awareness of the significance of a power rating (Watt-hours) of a battery or power bank; safe battery handling, charging and storage; enforcing safe passenger handling of lithium batteries; awareness of any national security regulations that prohibit power banks and spare lithium batteries in airliner cabins; and practicing current skills approved for fighting lithium battery fires in the cabin.
More than 20 years of in-flight experience shows that the probability of lithium-battery fires occurring anywhere, especially in flight operations, remains low but the potential severity is high. In thermal runaways, burning batteries ignite adjacent batteries, and may ignite surrounding combustible materials. Investigators of incidents aboard transport-category aircraft typically find that — in the worst cases — they involve flames, smoke, fumes and repeated explosions that eject extremely hot gases and molten-metal electrolyte from batteries, potentially causing severe injuries and significant damage. Thermal runaways always concern aviation safety researchers. This prolonged chemical reaction can be triggered by a short circuit, improper use of batteries or PEDs, physical abuse, failure of protective systems, manufacturing defects or extreme external heat. Historically, thermal runaways have been startling and disorienting for unwary crewmembers and passengers, and in safety experiments, resultant fires were especially hazardous when they spread to hidden areas of aircraft.
Compliance by lithium-battery manufacturers and users with all technical precautions, safe-handling instructions and firefighting practices still play a highly significant role in the low probability of serious in-flight incidents, numerous authorities say.
Overall, according to a 2016 magazine article by Airbus experts, “The air industry has become more aware of the specific characteristics of lithium batteries, and the associated risks can now be mitigated. Procedures have been developed to address the risks for lithium batteries being part of the aircraft design, those belonging to passengers’ or crews’ carry-on items, or indeed procedures linked to the shipping of lithium batteries as cargo. … A good awareness of risks posed by lithium batteries [among] both airlines’ personnel and their passengers is crucial.” Specific details about various types of lithium batteries must be considered to correctly manage their risks, the authors said.
The article notes that in the early years of investigating lithium battery–powered smoke-fire-fumes incidents in aircraft cabins, causal factors included faults allowing internal short circuits tied to design, manufacturing, component integration and packaging shortcomings. These causal factors were less frequent than human factors, especially so-called “user abuses” comprising negligence, failure to comply with technical instructions, and physical damage to batteries from accidents and careless mishandling. In the past 10 years, efforts to increase passenger awareness of lithium battery risks and compliance with restrictions have focused on airline-passenger mutual responsibility for mitigating the risk.
The following basic safety principles, with few changes since the arrival of the entirely new devices beginning around 2015, still apply to the environment of typical passenger aircraft:
- Follow rules about what can be carried and what cannot be carried in checked passenger baggage;
- Buy lithium batteries only from reputable sources that meet international safety-test standards (no recalled/damaged products or counterfeits);
- Only carry PEDS with lithium batteries installed in carry-on baggage; and,
- Protect lithium batteries (whether installed in a PED or as a spare) against short circuits and accidental crushing/damage (i.e, exposure to manual or electric seat mechanisms that can cause overheating and thermal runaways).
International lithium battery requirements for states and safety recommendations aimed at airlines also address the quantity of PEDs and lithium batteries carried by individual passengers and crewmembers for their personal use.
Normally, PEDs and spare lithium batteries with power less than 100 Watt-hours are permitted without a limit on quantity (for non-rechargeable lithium-metal spare batteries, however, the limit is a total weight of 2 gr of lithium-metal content). Lithium batteries of higher power capacity are limited to one installed in a device and two spares, limited to approved professional uses and possibly subject to advance approval of carriage by the airline or a security agency.
The following definitions explain terms common to safety-awareness campaigns by the International Air Transport Association (IATA), Flight Safety Foundation (FSF) and other organizations regarding spare lithium battery concerns that began to emerge around 2015:
- Smart bags and smart luggage — These suitcases and other types of luggage may contain a rechargeable lithium battery that powers built-in features, such as an electronic lock, electronic baggage tag, power bank, electric motor–driven wheels for self-propelled rolling or sitting/stand-up riding, bag-weighing system, satellite-based trackers with or without GSM telephone connectivity and Bluetooth, RFID and Wi-FI network compatibility with other devices.
- Power banks — Also called by terms such as external power pack and mobile battery, these portable devices charge consumer devices such as mobile phones and tablets. IATA Dangerous Goods Regulations (DGR) classify power banks as batteries and they must be assigned under DGR to UN 3480, Lithium-ion Batteries, or UN 3090, Lithium-metal Batteries, as applicable. IATA’s 2019 lithium-battery guidance says, “For carriage by passengers, power banks are considered spare batteries and must be individually protected from short-circuit and carried in carry-on baggage only.”
- Spare lithium batteries — Lithium batteries (including power banks, as noted) are regarded as “spares” while stowed external to the PED in protective packaging (such as in original packaging, in a heavy-duty plastic bag or with terminals/connectors insulated by adhesive electrical tape suitable for preventing a short circuit of the terminals).
- Trackers — These devices use satellite-based positioning data or other data-network technology for determining the location of the attached bag, which also enables a self-propelled smart bag to autonomously follow its owner. The key safety considerations are that the airline must approve each device to prevent interference with navigation systems, and the tracker must be powered off at all times during flight operations. If lithium batteries are removed from trackers to power off the device, they must be safety carried, protected and stowed like other spare lithium batteries.
- Electronic baggage tags (EBTs) — These devices typically are powered by non-lithium AA-size batteries and thus do not fall under lithium-ion battery restrictions. However, if non-rechargeable lithium-metal AA-size batteries are used, rules for PEDs with installed batteries apply. EBTs use passive RFID signal-reception technology and QR codes to briefly activate, capture the passenger’s journey information from airlines and deactivate under protocols defined by the International Air Transport Association’s (IATA’s) Recommended Practice 1754.
- Electric scooters — These lithium battery–powered, personal transportation devices (PTDs, also called by brand names or called self-balancing scooters or balance wheels among many terms) are for recreational use — unlike wheelchairs and other conventional mobility aids for use by passengers with reduced mobility. (Typical mobility aids have a battery of 300 Watt-hour capacity.) PTDs and spare lithium batteries for them were banned by more than 50 airlines in 2016 after an airline investigation found that some PTDs used poorly labeled lithium-ion batteries, some exceeding 160 Watt-hours, which are forbidden from being transported in either the checked baggage of passengers or crewmembers, or in their carry-on baggage.
Smart Bags and Other Disruptive Devices
ICAO’s recommendations to states — in response to the initial 2017 marketing of smart bags to consumers in many countries — have been communicated to airlines and airline passengers through a media campaign by IATA in website articles and videos.
The campaign explains why lithium batteries must be removed from the smart bag and safely packaged and stowed in the cabin as any other spare battery. Smart bags without removable lithium batteries — under a typical airline’s adoption of international safety recommendations — are prohibited as checked luggage and the airline may not be able to accommodate the smart bag as a carry-on bag for various practical reasons.
IATA’s campaign also reminds passengers that PEDs with lithium batteries installed always should be carried as carry-on luggage. “Passengers can carry personal electronic devices in checked baggage, although it is recommended that all devices with installed batteries be carried in the cabin,” IATA says, “Any devices in checked baggage must be completely turned off, not left in hibernation or sleep mode. The device must be packed in the bag so that it is protected against damage and should not be packed next to flammable items such as aerosols or perfumes.”
Spare lithium-ion, lithium-metal and lithium-polymer batteries — including external battery packs of these types — are prohibited from carriage as checked baggage, according to FAA guidance cited in FSF articles.
Changes in ICAO’s Technical Instructions for the Safe Transport of Dangerous Goods by Air 2019-2020 — noted for possible relevance to emerging issues affecting spare lithium batteries in the cabin — include:
- Addition of new classification criteria for lithium batteries containing both primary lithium metal cells and rechargeable lithium-ion cells;
- A revision forbidding the transport of lithium cells or batteries that cannot be diagnosed as damaged or defective prior to transport;
- Addition of provisions allowing for the transport of lithium batteries on passenger aircraft under specified conditions;
- Classification criteria for and restrictions on lithium content for lithium metal and total capacity for lithium-ion for batteries containing both primary lithium metal and rechargeable lithium-ion cells;
- New provision for vehicles and battery-powered equipment and vehicles;
- Revisions to provisions for dangerous goods carried by passengers or crew, including addition of restrictions for baggage equipped with lithium batteries;
- Addition of new restrictions for battery-powered portable electronic smoking devices; and,
- Revisions to proposed new training provisions.
Accidents and Incidents
On 10 February 2007, smoke was observed coming from an overhead locker on an Airbus A320 which had just departed from New York JFK. It was successfully dealt by cabin crew fire extinguisher use whilst an emergency was declared and a precautionary air turn back made with the aircraft back on the ground six minutes later. The subsequent investigation attributed the fire to a short circuit of unexplained origin in one of a number of spare lithium batteries contained in a passenger's camera case, some packaged an some loose which had led to three of then sustaining fire damage.
B738 diversion into KCOS following in-flight fire. The fire started after a passenger's air purifier device caught fire whilst in use during the flight. The user received minor burns and the aircraft cabin sustained minor damage.
- “Transport of Lithium Metal and Lithium Ion Batteries” in 2019 Lithium Battery Guidance Document, Revision 1, by International Air Transport Association (IATA), December 12, 2018. (Revised per the 2019-2020 edition of the ICAO Technical Instruction for the Safe Transport of Dangerous Goods by Air (Technical Instructions) and the 60th edition of IATA Dangerous Goods Regulations (DGR). [link to online store]
- “Passenger/Crew Baggage,” Chapter 4 in Lithium Battery Risk Mitigation Guidance for Operators, 2nd Edition, by IATA, 2016.