BB-609: Lithium Battery CAUTION and Overpack Labels for Air Transport

Lithium-ion and lithium-metal cells and batteries are regulated as dangerous goods for transport because stored electrochemical energy can create fire and thermal runaway hazards if a cell is short-circuited, damaged, improperly packed, or exposed to abusive conditions. Air transport is especially controlled, and shippers must follow the current IATA Dangerous Goods Regulations together with applicable national rules, operator variations, and carrier policies.

Older lithium battery shipping references often use terms such as CAUTION label or Lithium Battery Handling Label. Those terms remain common in legacy documentation and warehouse procedures, but the required mark or label for a real shipment must be checked against the current regulation, the correct UN number, and the applicable packing instruction. A label that was acceptable under an earlier edition may not be sufficient for a current air shipment.

General Lithium Battery Transport Requirements

The first step is to identify exactly what is being shipped. Lithium batteries are not handled as a single generic category. Requirements change depending on whether the shipment contains loose cells or batteries, batteries packed with equipment, batteries contained in equipment, lithium-ion chemistry, lithium-metal chemistry, quantity limits, watt-hour or lithium-content thresholds, and whether the shipment qualifies for a reduced-requirement section or must move as fully regulated dangerous goods.

For lithium-ion batteries, common IATA packing instruction references include:

For lithium-metal batteries, the corresponding loose-battery instruction commonly referenced is PI 968 for UN 3090. The exact instruction must be confirmed before packing or labeling because the marks, labels, documentation, quantity limits, and aircraft restrictions can differ substantially.

Short-circuit protection is a core requirement. Each cell or battery must be protected so that conductive parts cannot bridge the terminals during normal transport handling. Practical methods include non-conductive inner packaging, individual plastic bags, terminal caps, recessed terminals, tape over exposed terminals where appropriate, and dividers that prevent battery-to-battery contact. The package should not allow loose cells to tumble together, contact metal tools or hardware, or shift into a position where the terminals can touch conductive surfaces.

Short-circuit prevention is not only a labeling issue; it is a package-design issue. A compliant outer label does not make an unsafe inner package acceptable. The inner packaging should keep each cell or battery separated, immobilized, and protected from crushing or abrasion. If multiple batteries are inside one package, they should be arranged so that normal vibration, drops, and sorting impacts cannot defeat the terminal protection.

Battery packs may require their own approval or compliance evidence. A pack is not automatically acceptable for transport simply because its individual cells are approved or sourced from a reputable cell manufacturer. The assembled pack can introduce new risks through interconnects, protection circuitry, enclosure design, fusing, insulation, or mechanical layout. Modified packs require particular attention because a change in configuration may invalidate prior compliance assumptions. Shippers should maintain the applicable approval or compliance documentation for the product actually being transported, not only for the cells inside it.

Marks and labels must match the shipment. Depending on the packing instruction, section, quantity, aircraft mode, and regulatory status, a lithium battery package may need one or more of the following:

• a lithium battery mark or applicable handling mark;
• the correct UN number, such as UN 3480, UN 3481, UN 3090, or UN 3091 as applicable;
• a Class 9 lithium battery hazard label where the shipment is regulated as Class 9 dangerous goods;
• a Cargo Aircraft Only label where passenger-aircraft carriage is not permitted;
• shipper and consignee details and other dangerous goods marks where required;
• contact information if required by the applicable rule set, carrier, or legacy handling-mark procedure;
• the word OVERPACK when required marks and labels on the inner packages are not visible through the overpack.

The older “CAUTION” wording should therefore be treated carefully. It may describe a legacy lithium battery handling label used for shipments that were exempt from the full Class 9 dangerous goods label but still needed communication to handlers. Current shipments should not rely on the word CAUTION alone. The package should display the current lithium battery mark or hazard label required by the applicable IATA packing instruction and section.

Overpacks require visibility or repetition of marks. An overpack is an outer handling unit used to consolidate one or more packages. If the required labels and marks on the packages inside the overpack remain clearly visible, they may not need to be duplicated solely for visibility. If they are not visible, the required labels and marks representative of the contents must be repeated on the outside of the overpack, and the overpack must be marked with the word OVERPACK. This marking tells handlers and inspectors that the visible outside unit contains already prepared dangerous-goods packages.

The overpack must not be used to hide non-compliant packages. Each package inside the overpack must still be properly packed, marked, and labeled according to the applicable regulation. The overpack itself should maintain package integrity, prevent movement, and avoid creating new hazards such as crushing, conductive contact, or incompatibility between contents. Where compatible dangerous goods or non-dangerous goods are included in the same overpack, the shipper must ensure that the contents are allowed together and cannot react dangerously with each other.

The April 2016 rule change is still important historically because it limited how Section II PI 965 shipments could be consolidated. Guidance cited for PI 965 and PI 968 Section II states that a shipper is not permitted to offer more than one Section II package in a single consignment and that not more than one Section II package prepared under PI 965 or PI 968 may be placed in an overpack. When such a package is placed in an overpack, the required lithium battery handling label or mark and Cargo Aircraft Only label must either remain clearly visible or be affixed to the outside, and the overpack must be marked OVERPACK. Because lithium battery air-transport rules are updated frequently, these limits should always be checked against the current IATA edition and carrier variations before shipment.

Loose lithium-ion cells and batteries shipped under PI 965 also require special attention because current guidance has included a state-of-charge limit for UN 3480 shipments and restrictions on passenger-aircraft carriage. The shipper should not assume that requirements for batteries contained in equipment are the same as requirements for loose batteries. A laptop with a battery installed, a replacement battery packed beside a tool, and a carton of loose battery packs can fall under different instructions and different marks.

Defective, damaged, recalled, or unsafe batteries are not normal cargo. Batteries identified as defective and at risk of failing during transport are generally forbidden from normal air transport. This includes batteries that may overheat, ignite, short internally, vent, leak, swell, or enter thermal runaway under transport conditions. A cosmetic scratch on a case is not the same as a battery with evidence of electrical or thermal failure, but any suspected unsafe condition should be evaluated before shipment.

Recalled batteries require similar caution. A recall may be issued because a product has an elevated failure risk, and transport rules may prohibit routine air shipment or require special procedures. Shippers should not place recalled or suspect batteries into standard lithium battery packaging merely because the cells are small or because the package carries a lithium battery mark. Unsafe batteries may require special approval, specialized packaging, ground transport, disposal routing, or instructions from the appropriate authority.

Old batteries intended for disposal or recycling need separate review. End-of-life lithium battery products can be more variable than new products. Some may be deeply discharged, swollen, mechanically damaged, contaminated, previously overheated, or mixed with incompatible items. The reference guidance states that lithium battery products for disposal are forbidden from air transport unless approved by the appropriate authorities. In practice, recycling streams should be screened and sorted so that damaged, swollen, leaking, or suspect batteries are not mixed into routine air shipments.

Packing must protect the contents through normal handling. Where the applicable lithium battery provision requires it, each shipping package must be able to withstand a 1.2 m drop in any orientation without damaging the cells or batteries, causing them to shift in a way that creates a hazard, or releasing the contents. This requirement should be treated as a real design constraint, not as a paperwork detail.

A practical lithium battery package should include:

• secure inner packaging around each cell, battery, or device;
• cushioning to absorb shock and vibration;
• dividers or spacing where multiple batteries are present;
• terminal protection and non-conductive materials;
• a strong outer package appropriate for the weight and contents;
• void fill so that the contents cannot move freely;
• closure methods that remain secure during sorting and transport.

The package should also protect against crushing of equipment that contains batteries. If equipment is used as part of the protection system, the equipment should hold the battery securely and prevent stress on the battery compartment, wiring, or terminals. Accessories, tools, chargers, and spare conductive parts should not be allowed to contact battery terminals.

Quantity limits and package limits must be checked before offering the shipment. Reduced-requirement sections typically depend on limits for the number of cells or batteries per package, the number of packages per consignment, battery rating, and package mass. For Section II PI 965 and PI 968 shipments, guidance cited in the supplied material states that only one such package may be offered in a single consignment and only one such package may be placed in an overpack. These restrictions are easy to violate when warehouse staff consolidate several small cartons onto one pallet or into one master carton. The shipping process should therefore control not only the package label but also order consolidation, palletization, and consignment creation.

Batteries contained in or packed with equipment must be protected against accidental activation. Equipment should be switched off, secured, or designed so that it cannot turn on during transport. Activation can generate heat, discharge the battery, move mechanical parts, transmit signals, or create a fire risk if the device operates inside packaging without ventilation. Controls may include recessed switches, switch guards, lockouts, protective covers, software shutdown, removal of activation keys, or packaging that prevents pressure on buttons. The correct method depends on the equipment design.

Batteries packed with equipment but not installed in it need both battery protection and equipment protection. Spare batteries in the same package as a device must be individually protected against short circuit. They should not be loose in the box, even if the equipment itself is well protected.

Small consumer items can have reduced requirements, but they are not automatically unregulated. Very small devices such as watches, calculators, or similar products containing small cells may qualify for exceptions or reduced marking and documentation requirements when the cells are installed in the equipment and the package meets the applicable conditions. However, the shipper should verify the current regulation and the carrier’s policy. A carrier may impose stricter acceptance requirements than the base regulation, and the exception for a small installed cell does not necessarily apply to spare cells shipped separately.

The most reliable procedure is to classify first, then pack, then mark and label. Start with the chemistry and configuration, select the correct packing instruction, determine the applicable section, confirm quantity and aircraft restrictions, design the package for short-circuit and damage prevention, and only then apply marks and labels. If an overpack is used, confirm that all required package information remains visible or is repeated on the outside with OVERPACK clearly marked.

Lithium battery shipping failures often come from small process gaps: a warehouse combines two Section II packages into one consignment, a legacy CAUTION label is used after rules have changed, a phone number is omitted where a carrier still requires it, a battery pack is treated as approved only because its cells were approved, or an overpack hides the Cargo Aircraft Only label. These are preventable errors. For air transport, the final check should always be against the current IATA Dangerous Goods Regulations, the applicable packing instruction, and the accepting carrier’s latest lithium battery policy.

References

1. Battery University | BU-704b: CAUTION & Overpack Labels. (n.d.). http://www.batteryuniversity.com/article/bu-704b-caution-overpack-labels
2. The Complete Guide to CAUTION and Overpack Labeling for Lithium Battery Shipping. (n.d.). https://www.large-battery.com/blog/caution-overpack-labels-of-lithium-battery-shipping-guide
3. Overpack Label | (Labelling & Marking of Overpacks). Buy Online.. (n.d.). https://hibiscus-plc.co.uk/overpack-label
4. Overpack labels. (n.d.). https://www.isikkerhed.dk/butik/faresedler/10x10cm/overpack
5. Overpack Labels - ICC Compliance Center Inc - USA. (n.d.). https://www.thecompliancecenter.com/product-category/labels/shipping-and-handling/overpack/feed
6. Overpack packaging for dangerous goods - OVERPACK. (n.d.). https://en.overpack.it/news/overpack-packaging-for-dangerous-goods.html
7. SWE Lithium Ion Battery Pack Air Transport Requirements .... (n.d.). https://www.swe.com/files/638
8. Lithium Battery Packaging Requirements & Overpack Rules. (n.d.). https://www.rpmmoves.com/blog/lithium-battery-packaging-requirements
9. Battery guidance document. (n.d.). https://www.iata.org/contentassets/05e6d8742b0047259bf3a700bc9d42b9/lithium-battery-guidance-document.pdf
10. Hazardous Materials: Enhanced Safety Provisions for Lithium .... (n.d.). https://www.federalregister.gov/documents/2022/12/21/2022-27563/hazardous-materials-enhanced-safety-provisions-for-lithium-batteries-transported-by-aircraft-faa