Many battery types are categorised as Dangerous Goods in the applicable International Civil Aviation Organization (ICAO) Technical Instructions for the Safe Transport of Dangerous Goods (Doc 9284),and also in the International Air Transport Association (IATA) Dangerous Goods Regulations (DGR). The DGR are intended as a field document and have no legal standing but have been developed from the ICAO Technical Instructions which are the legal framework and are compatible with them, although sometimes more restrictive.
This categorisation as Dangerous Goods has been made because of the risk of fire from spontaneous battery ignition, whether batteries are installed in equipment at the time or not, and also because in some cases it is not possible to control any such ignition which might take place on aircraft using the fire control methods available. However, most of the batteries types carried by passengers for their personal use are routinely permitted under the “excepted quantities” provisions. The exact limits of such concessions may be more restrictive than the minimum provided by ICAO according to the domicile of a particular carrier, or according to rules set by the carrier itself. Permitted carriage is usually predicated upon quantity, type of flight (passenger or non-passenger) and, for passenger flights, whether the items are the cabin or checked baggage of passengers travelling on the same flight. Where spare or loose batteries are permitted, they must be carried or packed in such a way that they are protected from damage and short circuit. Short circuiting of any charged battery and subsequent overheating or sparking can occur if a metallic path capable of conducting electricity is established and maintained between terminals of opposite polarity.
Dry cell alkaline batteries, including the common AAA, AA, C, D, 9-volt and button cell types and dry cell rechargeable batteries such as Nickel Metal Hydride (NiMH) and Nickel Cadmium (NiCad) represent much lower quantifiable risk of fire provided that precautions against unintended activation or short circuiting of the terminals in loose packed batteries are taken. However, lithium-based batteries can be extremely flammable because of this and the much greater power contained within and are subject to restrictions on carriage both as cabin and checked baggage.
These are the type of batteries that most often feature in on-aircraft incidents. Often it is overheating, which eventually triggers ignition in equipment and batteries that, unknown to the user, are faulty in some way. However, various origins of overheating have been identified during investigations.
There are two principal types of lithium battery. Lithium metal batteries and Lithium ion batteries. Lithium polymer batteries are a kind of lithium ion battery and so are also included in that category. Fires arising in the Lithium Metal type cannot necessarily be extinguished using fire suppression equipment currently carried on aircraft. For this reason, the maximum permitted lithium content of this type is much smaller than for lithium ion types. However, when installed in serviceable equipment, the risk of overheating is assessed as low for both types and they may, in most circumstances, be carried by passengers in either cabin or checked baggage. No spare or loose lithium batteries of either type are usually permitted in accompanied checked baggage.
- Lithium Metal batteries (also referred to as non-rechargeable lithium or primary lithium) are batteries that cannot be recharged and are designed to be thrown away once their initial charge is used up. They are often used in cameras and in other small personal electronic devices (PEDs). Consumer-sized batteries of these types - typically those containing up to 2 grams of lithium per battery (which includes all the usual non-rechargeable batteries for personal film and digital cameras such as AA, AAA, 123, CR123A, CR1, CR2, CRV3, CR22, 2CR5, etc. and flat/round lithium-button cells) are not usually subject to restrictions in personal-use quantities. Passengers are usually prohibited from carrying larger batteries of this type.
- Lithium Ion batteries are also known as rechargeable lithium, lithium polymer, LIPO or secondary lithium batteries. They are always mains-rechargeable and are normally found in laptop computers, digital cameras, camcorders, cell phones, smart phones, tablet computers, and radio-controlled toys, and small remotely pilot aircraft, or drones. They may take the various forms including the standard AA, AAA, and 9-volt types. The degree of potential fire hazard from a lithium ion batteries increases in direct proportion to the amount of lithium it contains. However, since few batteries display this information, an approximate equivalence has been developed which links the watt-hours of battery power with the lithium content of these batteries. The watt hours (wh) which a particular battery provides can be checked by multiplying the placarded milliamp hours (mAh) by the placarded volts (V). Lithium content is approximately 8 grams per 100 watt hours. Most lithium ion batteries currently available to consumers have a power output below 100 watt-hours and the number of these that can be carried in passenger baggage when installed in equipment is not limited. A small number of very large / extended life computer laptop batteries and some batteries used for powering professional audio-visual equipment have ratings of up to 160 watt-hours and are usually restricted to a maximum of two per passenger. For lithium contents greater than this, there are no concessions for carriage in passenger baggage.
It should be noted that some more complex issues may be raised if passengers are able to connect their battery powered equipment to an aircraft power source since such action usually has the concomitant effect of initiating a recharge of the battery supply. At the first hint of battery overheat – the equipment feeling hotter than usual or a ‘hot’ smell – the power cable should be disconnected and the equipment placed in view.
As lithium ion batteries are rechargeable they represent the greatest number of batteries on a passenger aircraft. It is entirely possible for a single aisle airliner with 140 passenger seats to have in excess of 500 lithium batteries onboard. This presents a threat not only due to the number but also to the potential difficulty in gaining access during a thermal runaway/overheat. Regulators are updating guidance to crewmembers in the best actions to fight such fires. Movement of overheating electronic devices can cause adjacent cells to overheat resulting is high-energy expulsion of extremely hot gel and parts of the device acting as shrapnel. It is therefore imperative that adequate protection of the crewmember acting as the firefighter be provided. Only if adequate protection is available should a device be moved.
Cooling an overheating device is the only way to stop the thermal runaway. Water or other non-alcoholic liquids in large quantity will be necessary. The crew must consider the potential collateral damage of a large amount of liquid. If, in their professional opinion, it is a safer course of action to move the device, protection of the firefighter and a clear plan of where to contain the device must be accomplished. During thermal runaway lithium batteries will emit significant amount of organic vapor (looking like smoke) it is a mucous membrane irritant and high flammable. In addition the odour of these fumes is noxious and very unpleasant. Containment of the device to eliminate fumes and the potential injury by additional cell discharge is essential.
Carriage of Lithium Batteries as Cargo
Under the ICAO Technical Instructions, lithium batteries shipped as cargo attract standard dangerous goods status. Specific packaging requirements and maximum quantity per package apply according to classification. The classifications are:
- UN3480 Lithium ion batteries (including Li-ion polymer batteries)
- UN3481 Lithium ion batteries contained in equipment or packed with equipment (including Li-ion polymer batteries)
- UN3090 Lithium metal batteries (including lithium alloy batteries)
- UN3091 Lithium metal batteries contained in equipment, or packed with equipment (including lithium alloy batteries)
A Safety Alert for Operators (SAFO) issued by the FAA on 8 October 2010 summarises the recent research that shows that lithium metal (non-rechargeable) and lithium-ion (rechargeable) batteries are highly flammable and capable of igniting during air transport. Ignition of lithium metal batteries can be caused when a battery short circuits, is overcharged, is heated to extreme temperatures, is mishandled (including being crushed or dropped), or is otherwise defective. (Around one in 10,000,000 is acknowledged to be potentially defective during manufacture.) Once a cell is induced into thermal runaway, either by internal failure or by external means such as heating, over-discharge 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.
Safety Alert for Operators (SAFO) 16004, issued by the FAA on 06 May 2016 informs the operators of the new Dangerous Goods/Hazardous Materials requirements contained in ICAO Technical Instructions (TI) for the shipment of lithium batteries. This SAFO also encourages operators to notify their customers who offer lithium battery cargo shipments of these changes. For shipments subject to the ICAO Technical Instructions, the following provisions, which are applicable to both cargo transporters and operators, became effective on April 1, 2016:
- Shipments of UN 3480 Lithium Ion Batteries, including lithium ion polymer batteries, are FORBIDDEN from transport as cargo on passenger aircraft. These shipments must now have the “Cargo Aircraft Only” label in addition to existing hazard communication requirements.
- Shipments of UN 3480 Lithium Ion Batteries, including lithium ion polymer batteries “must be offered for transport at a state of charge not exceeding 30 percent of their rated capacity. Cells and/or batteries at a state of charge greater than 30 percent of their rated capacity may only be shipped internationally with the approval of the State of Origin and the State of the Operator under the written conditions established by those authorities”.
- Shippers of UN 3480 Lithium Ion Batteries, including lithium ion polymer batteries, and UN 3090 Lithium Metal Batteries, including lithium alloy batteries, under ICAO’s “Section II” provisions (for Packing Instruction (PI) PI 965 and PI 968) are not permitted to offer for transport more than one Section II package in any single consignment or more than one Section II package per overpack.
SAFO 16004 also emphasizes that "the safe transport of hazardous materials by air requires compliance from both shippers and operators".
Carriage of Battery Powered Wheelchairs as checked baggage
Although the majority of battery-powered wheelchairs carried in holds are powered by a gas-electrolyte which is non-spillable, incident experience suggests that the loading supervision associated with their carriage may not always achieve the necessary minimum standards.
The essential requirements for hold stowage must be met if hazardous outcomes are to be avoided:
- The battery must be securely attached to the wheelchair they power.
- The motor must be protected from inadvertent operation by positive deactivation using whatever method applies. It should be made particularly clear to loaders that application of the brake is not sufficient.
- The battery must be protected from a short circuit - this may be achieved if the battery is routinely contained in a box attached to the wheelchair
- Stowage must be such as to preclude damage to the associated wiring as a consequence of the in-flight movement of baggage or other hold contents.
It should be noted that the applicable ICAO Instructions do not require disconnection of non-spillable batteries because it is often very difficult to do and, if not done properly, can increase the risk of a fire. Only if deactivation cannot be achieved should disconnection be considered. If this is done, the battery terminals must be protected against short circuit, for example by the effective insulation of exposed terminals.
If spillable batteries are encountered, reference should be made to the restrictions detailed in the Technical Instructions.
Carriers must make every effort to ensure that passengers are aware of the requirements for carriage of batteries in their cabin or checked baggage. This can be difficult to achieve and carriers are advised to have appropriate checks in place to detect the degree of non compliance. Particular attention should be given to the appropriate packing of spare batteries which must be individually not loose packed or in their original packaging. This can limit the hazardous effect of a single - and unpredictable - single battery internal fault.
The latest edition of the ICAO publication "Emergency Response Guidance for Aircraft Incidents Involving Dangerous Goods" provides guidance on dealing with incidents in the aircraft cabin involving lithium battery powered equipment: Personal Electronic Device Fire - Cabin Crew Checklist. Some of the background to the issues involved is contained in an earlier UK CAA Paper 2003/4 (see Further Reading).
RAeS and Air Pilots The Royal Aeronautical Society and the Honourable Company of Air Pilots jointly revised and re-issued valuable reference documents on this topic, which should be used as first references for flight crew on this topic:
- Smoke, fire and fumes in transport aircraft, past history, current risks and recommended mitigations - Part 1:References, Fifth Ed., 2018, Royal Aeronautical Society.
- Smoke, fire and fumes in transport aircraft, past history, current risks and recommended mitigations - Part 2:Training, Second Ed., 2018, Royal Aeronautical Society.
- ICAO Doc 9284 ‘Technical Instructions for the Safe Transport of Dangerous Goods by Air’ issued biennially (current edition 2021-2022) and subject to regular amendment.
- ICAO Doc 9481 Emergency Response Guidance for Aircraft Incidents Involving Dangerous Goods (202021-2022 edition) subject to regular amendment.
- Guidance Material, ICAO website
FAA Research Reports