Altor guide · 2026-09-10

Overpacks: the word that changes your marking requirements

The fibreboard boxes are already legal. UN 1090 Acetone, Class 3, packing group II, packed to passenger packing instruction 353 at 5 L each. The dock then wraps three of them on a pallet so they move as one handling unit. The film hides the Class 3 diamonds and the UN numbers. The acceptance desk at the cargo terminal never sees the marks the packages already earned. The freight stops.

What the regulation actually requires

An overpack is not a package. 49 CFR 171.8 defines it as an enclosure used by a single consignor to protect a package, to make handling easier, or to consolidate two or more packages. That same definition excludes a transport vehicle, a freight container, and an aircraft unit load device. The dock examples are a pallet secured by strapping or stretch film, or a protective box or crate. PHMSA interpretation 24-0080 (20 December 2024) said wrapping already built overpacks onto a second pallet is still an overpack.

ICAO TI Part 1, Chapter 3 uses the same idea for air: an enclosure used by a single shipper to form one handling unit. IATA DGR 5.0.1.5 is the packing subsection for that unit. Each package inside still has to be packed, marked, and labelled as if it were going to travel alone. Packages that IATA DGR Table 9.3.A will not let sit together cannot sit in the same overpack. 49 CFR 173.22 still places classification on the offeror.

49 CFR 173.25(a) is the US overpack rule. Inner packages still have to meet 49 CFR 173.21 and 173.24. 173.25(a)(2) requires the proper shipping name, identification number, and labels for each hazardous material, unless marks and labels representative of each material remain visible. 173.25(a)(3) requires packages subject to 49 CFR 172.312 to sit with filling holes up, and requires orientation arrows on two opposite vertical sides of the overpack. 173.25(a)(4) requires the word OVERPACK when specification packagings are required, unless the specification markings representative of each package type are visible. Letters at least 12 mm (0.5 inches) high. 173.25(a)(5) forbids overpacking packing group I Class 8 corrosives or packing group I Division 5.1 oxidizers with any other materials. 173.25(a)(6) requires the 49 CFR 172.315 limited quantity mark unless a representative mark is visible, and the reduced 25 mm mark is not authorized on an overpack. 173.25(a)(7) does the same for the excepted quantity mark in 49 CFR 173.4a.

Air writes the same communication in ICAO TI Part 5, Chapter 2, 2.4.10. Unless marks and labels representative of all dangerous goods in the overpack are visible, mark OVERPACK in letters at least 12 mm high, and mark and label as required for each item. IATA DGR 7.1.7.1, 7.1.7.2, and 7.2.7 are the 67th Edition mapping. IATA DGR 7.1.7.3 requires identification marks when more than one overpack is used. IATA DGR 8.1.6.9.2, Step 7, requires Overpack Used on the Shipper's Declaration immediately after the packages in that overpack.

A worked example. Two combination packages of UN 1090 Acetone, Class 3, packing group II, each at 5 L under packing instruction 353, stretch wrapped on a pallet. If the Class 3 labels, UN 1090, and Acetone are not visible through the film, the overpack has to carry them, plus OVERPACK in 12 mm letters, orientation arrows if 172.312 applies, and Overpack Used on the declaration. Add a box of UN 1263 Paint, packing group II, also packing instruction 353 at 5 L, and both names and both identification numbers are required unless a representative set for each material stays visible.

The mistake people make

Desks treat the wrap as warehouse furniture. The inner specification boxes are correct, so the pallet is assumed to inherit that correctness. The film hides the diamonds. Nobody writes OVERPACK. Nobody writes Overpack Used. IATA DGR 9.1.3 fails the unit before anyone opens a box. They put the 25 mm limited quantity mark on the overpack, which 173.25(a)(6) does not allow. They overpack a packing group I corrosive with a solvent carton, which 173.25(a)(5) forbids. They treat an aircraft unit load device as an overpack, which 49 CFR 171.8 says it is not.

A missing OVERPACK mark is a paperwork failure that parks freight at the cargo terminal. What to do after a rejection sits at https://altor.consulting/rejected.html.

How to fix it

Decide whether 49 CFR 171.8 applies before anyone stretches film. If a single consignor is consolidating closed packages onto a pallet or into a crate, it is an overpack.

Keep the inner packages legal first. UN number, packing group, packing instruction, net quantity, marks, and labels on each package, as if the wrap will never exist. For UN 1090 packing group II on a passenger booking, that is packing instruction 353 at 5 L, or Y341 at 1 L if the limited quantity regime actually applies.

Look through the film. If the required marks and labels representative of each hazardous material, and the specification marks when 173.25(a)(4) applies, are clearly visible, you may not need to reproduce them. If they are not visible, put the proper shipping name, identification number, hazard labels, limited quantity mark if used, OVERPACK in letters at least 12 mm high, and orientation arrows on two opposite vertical sides, on the overpack itself.

Write Overpack Used on the Shipper's Declaration per IATA DGR 8.1.6.9.2, Step 7. If there is more than one overpack, add the identification marks IATA DGR 7.1.7.3 wants. Walk the paper against the unit in the same order IATA DGR 9.1.3 will. If you cannot stand behind that unit under 49 CFR 172.204 and IATA DGR 8.1.6.12, do not tender it.

Do not offer a wrapped pallet whose marks the desk cannot read.

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