# UN Certified Packaging: How to Read the Mark and What It Obliges _Eight fields, three tests, and a closure instruction most buyers never file._ **The short answer** **The mark is eight separate claims, not a grade.** It names the packaging type, which packing groups it passed, its mass or density limit, the year, the country and the maker. **It certifies a configuration rather than a box.** The closure counts as part of what was tested, and the shipper has to keep the closure instructions on file. A fiberboard box rated for dangerous goods carries a line of characters that looks like a product code. It is closer to a test certificate, and it describes a package that passed specific tests in a specific condition. Most published explanations decode it correctly. Almost none of them cite the rule behind it, which matters because the duties that follow the mark are federal, and inspectors check them. This reference covers each element of the mark and what the package had to survive. It also covers why the closure forms part of the certification, and the records a shipper has to produce on request. - **4G** - Fiberboard box - **X / Y / Z** - Packing groups passed - **1.8 / 1.2 / 0.8 m** - Drop heights - **90 days** - Records on demand > Figure: Each field is a separate assertion. Reading them together describes one tested package, not a quality level. ## Reading the Mark The code does the first job, and under the [code list](https://www.law.cornell.edu/cfr/text/49/178.502) the opening numeral names the form while the letter names the material. A 1 is a drum, a 3 a jerrican, a 4 a box, a 5 a bag and a 6 a composite packaging. Letters cover the materials, where A is steel, C natural wood, G fiberboard, H plastic and P glass or stoneware. So 4G reads as a box made of fiberboard, and 1A as a steel drum. The pattern holds across the whole family once those two tables are in hand. What follows depends on contents. The [marking section](https://www.law.cornell.edu/cfr/text/49/178.503) calls for specific gravity and a test pressure in kilopascals on liquid packagings. Solids and inner packagings instead show a maximum gross mass in kilograms and the letter S. ## X, Y and Z Are a Ladder One letter carries the performance claim, and it reads downward rather than as a category. X marks a design that passed the Packing Group I, II and III tests, while Y covers Groups II and III and Z covers Group III alone. Each letter therefore includes the groups beneath it. A Y box covers Group II and Group III material, so finding Y on a box holding a Group III substance is correct rather than an overspec. The reverse never works. A Z box cannot take Group II material, because nobody ever ran that design through the Group II tests. ## What the Package Had to Survive The letters stand on finished tests, and the rule prints every figure rather than leaving it to the lab. Dropping comes first. The [drop test](https://www.law.cornell.edu/cfr/text/49/178.603) calls for 1.8 m at Packing Group I, 1.2 m at Group II and 0.8 m at Group III. Plastic packagings go in at −18 °C or lower. Boxes take five samples rather than one. The drops run flat bottom, flat top, long side, short side and corner. Other forms carry their own sample counts, and drums take six samples across two drop sets. A single-ply bag with a side seam takes three samples and three drops apiece, on the wide face, the narrow face and the ends. The outer packaging may not leak at all. A slight leak from an inner closure still passes, provided it stops at once after impact and does not go on. | Test | Parameter | Pass condition | | --- | --- | --- | | Drop | 1.8 m (PG I), 1.2 m (PG II), 0.8 m (PG III); plastics at −18 °C or lower | No leakage from the outer packaging | | Leakproofness | Not less than 30 kPa for PG I, 20 kPa for PG II and III, held five minutes | No air escapes | | Stacking | Load of identical packages to a 3 m stack, for 24 hours | No leakage, no distortion that weakens the stack | Liquid packagings add an air test. [Leakproofness](https://www.law.cornell.edu/cfr/text/49/178.604) applies not less than 30 kPa to Group I packagings and 20 kPa to Groups II and III, held a minimum of five minutes. One exemption applies there. Inner packagings of combination packagings skip the air test, since the outer packaging does that job, and inner receptacles of composite packagings may be tested on their own instead. Stacking closes the set. The [stacking test](https://www.law.cornell.edu/cfr/text/49/178.606) loads a sample with the weight of identical packages stacked to at least 3 m, then holds it for 24 hours. Some packagings sit far longer. Certain plastic and composite liquid packagings run 28 days at 40 °C or above, which turns a day's test into a month's. Passing means more than staying dry. A sample must show no warp likely to cut its strength, upset a stack of packages or harm the inner packagings it holds. Periodic retesting may take a faster route, where a dynamic compression test stands in for the static hold and the greatest deflection must not top one inch. ## The Certification Covers a Configuration This is the part that catches people, because the mark belongs to a package as tested and the closure was part of that test. The rule is explicit about it. Under [section 178.2](https://www.ecfr.gov/current/title-49/subtitle-B/chapter-I/subchapter-C/part-178/section-178.2), a manufacturer has to supply closure instructions giving a consistent and repeatable means of closure. That method must close the packaging in the same manner as the tested sample. Read that standard carefully. Taping a 4G box the way the plant always tapes boxes is not compliance; closing it the way the test lab closed it is. The notification runs wider than tape. It has to cover the types and dimensions of the closures, including gaskets and any other components needed to pass the tests, plus closure instructions for inner packagings and receptacles. Air freight adds a line to that. Instructions for packages going by air must add guidance so the package, as packed for transport, holds up to the pressure differential rules. Changes are not banned outright. The testing rules allow six set variations, including cuts in outside dimensions of up to 25 percent, and inner packaging swaps that keep an equivalent level of performance. ## The Paperwork Is the Compliance Two parties carry duties, and they are not the same duties. The maker notifies each person it hands the packaging to, covering any rules of the part not met at the time of transfer, along with the closure information. The shipper carries the other half. Under [section 173.22](https://www.law.cornell.edu/cfr/text/49/173.22), whoever offers a hazardous material must determine the packaging is an authorized packaging, properly manufactured, assembled and marked. Records go with that, since a person must keep a copy of the maker's notice, closure instructions included, for non-bulk packages. A clock runs on producing them. Those records stay available for inspection by a Department representative, on request, for at least 90 days once the package goes to the initial carrier. Which reframes the buying decision, because ordering a marked box without filing its closure instructions leaves a paper gap that an inspection finds in minutes. ## Testing Does Not Stop at the First Batch A design does not get certified once and left alone. [Section 178.601](https://www.ecfr.gov/current/title-49/subtitle-B/chapter-I/subchapter-C/part-178/subpart-M/section-178.601) puts two clocks on it. Design qualification testing happens at the start of production of each new or different packaging. Periodic retesting then runs at least every 12 months for single and composite packagings, and at least every 24 months for combination packagings. The rule assigns duty plainly: the packaging maker has to assure that each package can pass the set tests. One test sample serves each test as a rule. A buyer can use that. Asking a supplier for the date of the most recent periodic retest is a fair question with a documented answer behind it. The answer also dates the stock. A box marked with a year several seasons back may still be compliant, yet it sits against a retest clock the buyer cannot see from the mark alone. ## Common Questions ### Does a UN mark mean a box is approved for a given material? Not on its own. The mark names which packing groups the design passed and what mass or density it was tested to. Which packagings a material may travel in comes from its own entry in the regulations, so classification decides first and the mark confirms second. ### Can a certified box be closed with any tape? No. The closure instructions have to give a repeatable method that closes the packaging the same way the tested sample was closed, covering closure types and dimensions including gaskets. Substituting a different tape or pattern departs from the tested configuration. ### What does the number after the X, Y or Z mean? For solids and inner packagings it is the maximum gross mass in kilograms. For liquids it is the specific gravity, followed by a test pressure in kilopascals, so a liquid mark and a solid mark are read differently. ### How long is a UN certification valid? There is no expiry on the mark itself, but the design has to keep passing. Periodic retesting runs at least every 12 months for single and composite packagings and every 24 months for combination packagings, which is a question worth putting to a supplier. **What this is and is not.** This is a reference to published federal requirements, not legal advice, and the controlling regulation governs any shipment. Material classification determines which packagings may be used in the first place. International modes add their own rules, so a package that complies at home does not comply by air or sea as a matter of course. **Key takeaways** - The mark is eight ordered claims: symbol, packaging code, performance letter, mass or density, solids or pressure, year, country and maker. - X covers Packing Groups I, II and III, Y covers II and III, and Z covers III alone, so each letter includes the groups beneath it. - Drop heights run 1.8, 1.2 and 0.8 metres by packing group, with plastics conditioned to −18 °C or lower and boxes dropped five ways. - Certification covers the tested configuration, and the closure instructions exist to reproduce how the sample was closed. - The shipper must retain the manufacturer's notification with those instructions and produce it on request for at least 90 days.