一批 UN1170（乙醇，Class 3，PG II）准备走全货机，工厂用了「我们一直在用的 4G 纸箱」装了 24 瓶 1L 玻璃瓶。货代验货时翻到外箱底，UN 规范标记写的是 4G/Z20/S/22/D/...——「Z」对应 PG III，而你这票货是 PG II。 这意味着这一整票货的外包装不合规。要么换箱重打包，要么改报 PG III（这是瞒报，风险更大）。客户那边还在催出货，工厂在国内、机场柜台在等单，你怎么办？ 这种事情每天都在国内大大小小的货代仓库里发生。原因不是包装太复杂，而是 PG 和 PI 之间的对应关系没人系统讲过。这一篇把 PG、PI、UN 规范包装码、性能测试这套体系一次性拆给你看。
一、PG 是「危险等级」，PI 是「调用入口」
DGL 表上你能看到每个 UN 号都对应了：
- 一个 PG（I/II/III，或没有）
- 两套 PI 编号：Passenger PI（客机）+ Cargo PI（全货机）
- 每套 PI 后面跟一个单件最大量
PG 决定了包装强度：PG I 最严，PG III 最松。 PI 决定了包装方式和限重：每个 PI 编号对应 DGR 第 5 章里一份具体的包装说明。
两者的对应关系是：
`` DGL 行 = UN + PSN + Class + PG → 对应 PI 编号 PI 编号 → 内/外包装允许清单 + 单件限重 + 特殊要求 UN 规范包装码 → 必须 ≥ 这一行 PG 要求的等级 ``
PG 不是你定的，是物质本身决定的，DGL 已经给出。PI 也不是你选的，是 DGL 表直接告诉你的。真正可以选的只有「具体哪一款 UN 规范包装」。
二、PG I/II/III 三档到底差什么
三档的核心差异在「包装能扛多大跌落、堆码、压力」。下表是工程语言而非法律语言，便于一线建立直觉：
| PG | 危险等级 | 对应包装等级标记 | 跌落测试基本要求 | 适用范围 |
|---|
| I | 高 | X | 最严，跌落高度最高 | PG I 货物专用，也可向下用于 II、III |
| II | 中 | Y | 中等 | PG II 货物可用，也可向下用于 III |
| III | 低 | Z | 最宽 | 只能用于 PG III 货物 |
Y 包装可以装 PG II 和 PG III，但绝对不能装 PG I。这是一线最容易出问题的方向——把 Y 包装当成「万能」包装。
要注意几个例外：
- Class 1（爆炸品）：不分 PG，按 Compatibility Group 走
- Class 2（气体）：不分 PG，按瓶式（cylinder）规范走
- Class 5.2 有机过氧化物 / Class 4.1 自反应物质：不分 PG，单独包装规则
- Class 6.2 感染性物质 A 类：不分 PG，走 PI 620 专用包装
- Class 7（放射性）：单独的 A 型 / B 型容器体系
其余 Class 3 / 4（部分子类）/ 5.1 / 6.1 / 8 / 9 都按 PG I/II/III 走。
三、UN 规范包装码怎么读：6 段字符的含义
这是空运 DG 包装一线最值钱的「读码能力」。
随便举一个真实样式：
`` UN 4G/Y15/S/24/D/BAM-12345 ``
拆成 6 段：
| 段位 | 字符 | 含义 |
|---|
| 1 | UN | 「这是 UN 规范包装」的标识 |
| 2 | 4G | 包装类型代码（4 = 箱，G = 纤维板纸箱） |
| 3 | Y15 | 包装等级 + 最大毛重（公斤）。Y = PG II/III 通用，15 = 最大 15 kg |
| 4 | S | 内含物类型（S = 固体或内包装；液体会写比重，如 1.4） |
| 5 | 24 | 制造年份（最后两位，例 2024 年） |
| 6 | D | 制造国国别代码（D = 德国） |
| 7 | BAM-12345 | 颁证机构 + 包装制造商编号 |
第 2 段「包装类型代码」常见组合
| 代码 | 类型 |
|---|
| 1A1 / 1A2 | 钢桶（闭口 / 开口） |
| 1H1 / 1H2 | 塑料桶（闭口 / 开口） |
| 3H1 / 3H2 | 塑料罐 |
| 4G | 纤维板箱（最常见的纸箱） |
| 4GV | 多用途纤维板箱（带额外内部缓冲） |
| 4H2 | 实芯塑料箱 |
| 6HA1 / 6HG1 等 | 复合包装 |
| 1G | 纤维板桶 |
| IBC（31HA1 等） | 中型散装容器 |
跨境电商高频用到的就是 4G（普通纸箱）和 4GV（带缓冲的多用途纸箱）。空运 Class 3 液体大部分是 4G + 内塑料瓶 + 吸收材料的组合。
第 3 段「包装等级 + 最大量」怎么读
- 字母：X / Y / Z = PG I / II / III
- 数字：
- 固体或内包装：最大毛重（公斤）
- 液体：最大比重（液体的密度上限）
如果你的货是液体，第 4 段会跟着写实测压力（如 100 表示 100 kPa）；如果是固体或内包装，第 4 段就写 S。
四、PI 内部结构：每一份 PI 都在讲什么
打开 DGR 第 5 章任何一份 PI，结构大致都是：
- 额外要求（特殊场景下额外加的条件）
- 客机最大量 / 全货机最大量（重复 DGL 表里的限重）
- 允许的单一包装清单（如果该 PI 允许单一包装）
- 允许的组合包装清单（内包装 + 外包装 + 单件限量）
- 特殊包装要求（如「内包装之间须用吸收材料隔开」「方向标签必备」）
举个具体例子——PI 353（客机，Class 3 PG II 液体）：
| 要求项 | 内容 |
|---|
| 客机单件最大 | 5 L（汇总值） |
| 允许单一包装 | 通常不允许（必须组合包装） |
| 允许的组合包装 | 玻璃 / 塑料 / 金属内瓶 + 4G 纸箱 / 4H2 塑料箱等外箱 |
| 内瓶限制 | 玻璃 ≤ 1 L、塑料 ≤ 5 L、金属 ≤ 5 L |
| 包装等级要求 | 外包装至少 Y（PG II） |
| 必备标签 | 主类标签 Class 3、方向箭头 |
PI 不是天书，它就是一张「内瓶 + 外箱 + 限量 + 必备标签」的组合菜单。看 3 份你就熟了。
五、单一包装 / 组合包装 / IBC / Overpack：四种形态
| 形态 | 含义 | 一线典型场景 |
|---|
| 单一包装（Single Packaging） | 1 个 UN 规范容器装内容物，外部就是它 | 钢桶装润滑油、IBC 装碱液 |
| 组合包装（Combination Packaging） | 多个内包装（瓶/罐）+ 1 个外箱 | 跨境电商最常见：玻璃瓶 + 4G 纸箱 |
| IBC（Intermediate Bulk Container） | 中型散装容器，通常 ≥1 m³ | 工业化学品、大件液体 |
| Overpack | 多个已合规包件再合装在 1 个外层（托盘 + 缠膜 / 大箱） | 拼箱、整托发货 |
Overpack 容易踩坑。规则不是把多个箱子缠一起就完事，而是：
- 外层必须能看到所有内层的危险品标签（要么穿透可见，要么在外层复印贴上）
- 外层必须用「OVERPACK」字样
- 内层每个箱子本身必须已经合规
六、性能测试：DGR 第 6 章在测什么
UN 规范包装在上市前要通过一套「击穿性」测试。一线不需要会做，但要会看测试报告判断这一款包装到底合不合规：
| 测试 | 目的 | 通过标准核心 |
|---|
| 跌落测试（Drop Test） | 模拟搬运中的撞击 | 不能有内容物泄漏（PG I/II 测试高度更高） |
| 堆码测试（Stack Test） | 模拟仓库堆放 24 小时 | 上层重量下不能变形/破裂 |
| 液压测试（Hydraulic Pressure Test） | 液体专用，测内瓶承压 | 通常 100 kPa 或更高，不能漏 |
| 气密测试（Leakproofness Test） | 液体单一包装专用 | 浸水气压下不能漏 |
包装制造商出厂时会给一份 UN Test Report。你在选型时建议向供应商索取这份报告，确认报告里的：
- 包装类型代码和你的 UN 规范码段位 2 一致
- 测试包装等级（X/Y/Z）满足你的 PG 要求
- 测试用的内容物比重和你的实际比重接近（液体）
- 测试日期在合理范围内（一般每 12 个月需要复验某些项）
七、4G vs 4GV vs 4H2：3 种主流外箱怎么选
跨境电商和工业出口的 DG 货，80% 用的是 4G、4GV、4H2 这三种外箱。它们看起来都是「箱」，但在 PI 适配、价格、强度上完全不同。
| 类型 | 全称 | 材质 | 强度特点 | 价格档 | 典型场景 |
|---|
| 4G | 纤维板箱 | 多层瓦楞纸 | 标准 | 最低 | 一般 PG II/III 液体，小批量 |
| 4GV | 多用途纤维板箱 | 瓦楞纸 + 内置缓冲材料 | 通用性强（一份认证可装多种内瓶） | 中 | 多 SKU 混装、电商小件 |
| 4H2 | 实芯塑料箱 | 注塑高密度塑料 | 抗潮、抗化学腐蚀 | 较高 | 高湿度环境、化学品强腐蚀场景 |
实战选型口诀：
- 单一稳定 SKU + 价格敏感 → 4G。但每换一种内瓶规格，技术上要重新匹配 UN Test Report。
- 多 SKU 混装、内瓶规格经常变 → 4GV。它的认证允许在一定范围内自由组合内瓶，省去每次重新匹配的麻烦。
- 目的地高湿、易溅水（海运拼柜、东南亚 / 南美航线） → 4H2。多花的钱换来的是不变形不渗水。
4GV 的隐藏价值：很多电商卖家不知道，4GV 的认证范围比 4G 宽得多。一份 4GV 认证可以同时覆盖玻璃瓶、塑料瓶、金属瓶的多种容量组合，只要满足认证文件里的「允许组合表」。一次采购，多种产品共用，长期看比 4G 更省。
典型选型场景对照：
- 选品：100ml 香水（PG II 液体）× 24 瓶/箱 × 月发 200 箱 → 选 4GV/Y15/S（一份认证覆盖多个 SKU）
- 选品：单一 SKU 1L 酒精消毒液（PG II 液体）× 12 瓶/箱 × 月发 50 箱 → 选 4G/Y20/S（成本最优）
- 选品：500g 工业固体氧化剂（PG II 固体）× 海运拼柜 → 选 4H2/Y30/S（防潮）
- 选品：单批次 500 瓶车间油漆稀释剂（PG III 液体）大件出货 → 考虑 IBC 而非组合包装
采购避坑：买 UN 规范箱要让供应商在合同里写明「附 UN Test Report 副本」+「箱印 UN 规范码与报告一致」。一些供应商会用「带 UN 字样的箱」鱼目混珠，实际无完整认证，到时候撕了印章你都没证据维权。
八、UN Test Report 怎么读：3 分钟核对要点
供应商给你一份 UN Test Report（多数是英文 + 颁证国语言），看起来一堆图表和数据，其实你只需要核对这几行：
| 核对项 | 报告里通常出现的位置 | 你要看的内容 |
|---|
| Packaging Type Code | 报告抬头 | 4G / 4GV / 4H2 等，要和外箱印的码一致 |
| Packing Group Tested | 抬头或测试条件 | X / Y / Z，要 ≥ 你货物的 PG |
| Inner Packaging Combinations | 中段表格 | 列出允许的内瓶规格组合，你的内瓶必须在里面 |
| Maximum Gross Mass | 测试条件 | 单件外箱可装最大毛重 |
| Specific Gravity | 液体测试条件 | 测试用液体的比重要 ≥ 你的实际比重 |
| Test Results | 末尾 | Drop / Stack / Hydraulic / Leakproofness 全部「PASS」 |
| Certificate Issuance Date | 抬头或末尾 | 1 年以内为最新，超过 2 年要追问是否仍有效 |
| Issuing Authority | 末尾盖章处 | BAM (DE) / DOT (US) / CAA (UK) 等，目的国认可 |
最容易栽的一项是「Inner Packaging Combinations」。你买了一款 4GV/Y20/S 外箱，但你装的内瓶不在它认证的组合范围内——技术上等于无认证。地服抽查时一对，整票货拒收。
跨境电商卖家如果是从工厂直接出货，建议每个 SKU 都让工厂提供对应的 UN Test Report 备份，存档至少 3 年，应对海关追溯。
九、吸收材料 / 缓冲材料：液体 DG 包装的隐形杀手
PI 353、PI 364 这类液体 PI 都有一条容易被忽略的要求：「当总量超过 X L 时，必须配置足以吸收所有内容物的吸收材料」。
吸收材料常见三类：
- 蛭石、硅藻土等矿物粉末
- 化学吸收棉（亲油 / 亲水分别选用）
- 防漏专用袋
新手最常犯的错：
- 用普通报纸或泡沫塑料当吸收材料 → 不达标
- 吸收材料量不足，理论上漏 1 瓶就漏出包装外 → 不达标
- 吸收材料和液体化学反应（如吸水材料碰强氧化剂）→ 危险
正确做法：按内瓶最大容积 × 1.0 倍准备吸收材料（保守一些可以 1.2 倍），并核对与货物的化学相容性。
十、Limited Quantity（Y 前缀 PI）：能走「半豁免」的捷径
DGL 表里如果一行的「Ltd Qty PI」列有值，比如 Y341，这就告诉你：这一票货如果按限量规则包装，可以走简化流程。
走 Limited Quantity 的好处：
- 包装强度要求降低（一般 Y 类纸箱即可）
- 不需要完整 DGD（部分目的国仍要简化版申报）
- 外箱用专门的 Y 标记（一个菱形，上下用黑色填充，上下尖端可以画一条横线，中间留白；规格不小于 100×100mm）
但要注意：
- 单件 + 内瓶都要小于限量阈值
- 仅限部分 Class 和 PG 适用
- 客机/全货机 Y 限量阈值不同，要看 DGL 对应列
- 不是所有 UN 号都允许走 Limited Quantity，看 DGL 该列是否有值
跨境电商如果选品集中在小规格液体（如 50ml 香水、100ml 酒精消毒液），走限量是非常划算的方式，但要严格控量。
如果你需要快速判断一票货能不能走限量、走限量的箱标怎么贴，可以用 OneCargoKit 的 Cargo Label Generator 直接生成对应 Y 标记和方向箭头模板，配合 Packing Size Advisor 算出来一个外箱装多少内瓶最合理。
十一、常见误区
- 误区 1：纸箱上看着有「UN」字样就是合规的 —— 错。UN 标记必须完整 6 段，缺一段都是无效。
- 误区 2：「Y」是通用万能箱 —— 错。Y = PG II/III，绝不能用于 PG I。
- 误区 3：组合包装的外箱合规就行，内瓶随便用矿泉水瓶 —— 错。内瓶也必须满足 PI 里指定的材质、容量、是否需要特定螺纹密封等要求。
- 误区 4：把多瓶液体装一个大塑料袋里再放外箱，就算「吸收」 —— 错。吸收材料是有具体化学要求的，塑料袋不吸收。
- 误区 5：限量货不用贴方向箭头 —— 错。所有含液体危险品的包件，无论是否限量，都要贴方向箭头。
- 误区 6：包装年份过期了仍能用 —— UN 包装从制造日起一般使用期限要按制造商规定 + DGR 要求评估。塑料容器尤其要注意老化。
- 误区 7：「OVERPACK」字样可以不写，反正一目了然 —— 错。规则明确要求外层标 OVERPACK + 内含件总数 + 总毛重。
- 误区 8：IBC 装液体危险品时不需要核对承压 —— 错。IBC 也要按 PI 的最大允许容量和承压等级走，且有定期复检要求。
十二、实操检查清单：包装核查 90 秒过一遍
- [ ] DGL 行已锁定，PG 已确认
- [ ] PI 编号已对应 Passenger / Cargo
- [ ] 外箱 UN 规范标记完整 6 段，等级（X/Y/Z）≥ PG 要求
- [ ] 外箱年份 + 国别 + 制造商编号清晰可见
- [ ] 内瓶材质、容量符合 PI 允许清单
- [ ] 内瓶密封方式符合 PI（部分需要带垫片螺纹盖）
- [ ] 液体已配置足量吸收材料 + 化学相容性核对
- [ ] 内瓶之间有充足缓冲（防碰撞）
- [ ] 单件总量未超 PI Passenger / Cargo 限重
- [ ] 主类标签 + 次类标签 + 操作标签 + 方向箭头齐备
- [ ] 限量货已贴 Y 标记
- [ ] Overpack 已标「OVERPACK」+ 件数 + 总毛重
- [ ] 工厂提供的 UN Test Report 已存档
十三、给三类岗位的判定方法
| 岗位 | 包装决策核心动作 | 输出 |
|---|
| 货代操作 | 验货时读 UN 规范码 + 比对 DGL PG | 是否接收、是否退回重包 |
| 跨境电商运营 | 选品时算单件容量是否能走限量 | 上架与否、单 SKU 包装方案 |
| 工厂 / 供应商 | 采购 UN 规范包装 + 索取 UN Test Report | 出货前包装合规 |
跨境电商规划包装时还要算一个经济账：用 4G/Y20/S 的箱子装 24 瓶 100ml，vs 用 4GV/Y15/S 的箱子装 20 瓶 100ml，哪个体积重 + 计费重最低？用 Chargeable Weight Calculator 跑一遍很快就有答案。
十四、合规与边界提醒
- 本文是基于公开的 IATA DGR 包装体系做的实操梳理，不构成法律、合规或安全建议
- UN 规范包装的具体性能测试方法、复验周期以现行版 IATA DGR 第 6 章为准
- 各国对 UN 规范包装的颁证机构不同（如德国 BAM、美国 DOT、英国 CAA），跨境采购包装时要确认证书在目的国 / 中转国均被认可
- 锂电池、感染性物质、放射性物质等品类的包装走专门 PI（如 PI 965-970、PI 620、PI 950 系列），本文未覆盖，需另行专题研究
- 强烈建议从具备资质的包装制造商采购，并保存好每批次的 UN Test Report
十五、结尾：包装合规是 DG 链路里「最便宜的合规投资」
很多人觉得 UN 规范包装贵，能省就省。算一次总账你会发现完全相反：
- 一个 4G Y 纸箱比普通纸箱贵几块钱，但一次包装不合规可能导致整票货被拒运、改派、目的港退回 + 客户赔偿
- 一份 UN Test Report 几乎零成本（工厂出厂时就给），但一次抽检时拿不出会被认定瞒报
- 一次吸收材料配置规范，能让一瓶 1 L 液体破损不波及整箱，避免地服当场拒收和地面污染清理
包装是 DG 全链路里成本最低、收益最高的一环。同时它也是最容易被外行（采购、供应商、新人操作）跳过的一环。把这一环管好，你的 DG 派工事故率会下降一个数量级。
下一篇我们继续往「合规链路」上走：标签、标记、方向箭头到底怎么贴，标贴位置、尺寸、颜色有哪些硬性规则，地服抽检最常打回的标签错误有哪些。我们下次见。
A shipment of UN1170 (ethanol, Class 3, PG II) was scheduled to be transported on a full-cargo flight. The factory packed 24 1-liter glass bottles into “the 4G cartons we’ve always used.” When the freight forwarder inspected the shipment and flipped the outer carton over, the UN regulation marking read 4G/Z20/S/22/D/...— “Z,” which corresponds to PG III, whereas this shipment is PG II. This means the outer packaging for the entire shipment is non-compliant. You must either replace the cartons and repack the shipment, or reclassify it as PG III (which constitutes misdeclaration and carries even greater risk).The client is still pressing for shipment, the factory is in China, and the airport counter is waiting for the shipment—what do you do? Situations like this happen every day in freight forwarders’ warehouses across China, both large and small. The reason isn’t that the packaging is too complicated; it’s that no one has ever systematically explained the relationship between PG and PI. This article will break down the entire system—including PG, PI, UN packaging codes, and performance testing—for you in one go.
I. PG Is the “Hazard Class,” PI Is the “Point of Entry”
On the DGL table, you’ll see that each UN number corresponds to:
- A PG (I/II/III, or none)
- Two sets of PI numbers: Passenger PI (passenger aircraft) + Cargo PI (all-cargo aircraft)
- Each set of PI numbers is followed by a maximum quantity per piece
PG determines the packaging strength: PG I is the strictest, and PG III is the least restrictive. PI determines the packaging method and weight limits: each PI code corresponds to a specific set of packaging instructions in Chapter 5 of the DGR.
The relationship between the two is as follows:
`` DGL 行 = UN + PSN + Class + PG → 对应 PI 编号 PI 编号 → 内/外包装允许清单 + 单件限重 + 特殊要求 UN 规范包装码 → 必须 ≥ 这一行 PG 要求的等级 ``
You do not determine the PG; it is dictated by the substance itself, as specified in the DGL. You also do not choose the PI; it is directly specified in the DGL tables. The only choice you truly have is which specific UN-compliant packaging to use.
II. What Are the Key Differences Between PG I, II, and III?
The core differences among the three categories lie in “how much impact, stacking, and pressure the packaging can withstand.” The table below uses engineering terminology rather than legal language to help frontline personnel develop an intuitive understanding:
| PG | Hazard Level | Corresponding Packaging Grade Marking | Basic Drop Test Requirements | Scope of Application |
|---|
| I | High | X | Most stringent; highest drop height | PG I: For cargo only; may also be applied downward to II and III |
| II | Medium | Y | Medium | PG II: Suitable for cargo; may also be used for Class III |
| III | Low | Z | Widest | Can only be used for PG III cargo |
Y packaging can be used for PG II and PG III, but absolutely not for PG I. This is the area where problems most commonly arise on the production line—treating Y packaging as a “one-size-fits-all” solution.
Note the following exceptions:
- Class 1 (Explosives): Regardless of PG, follow the Compatibility Group guidelines
- Class 2 (Gases): Regardless of PG, follow the cylinder specifications
- Class 5.2 Organic Peroxides / Class 4.1 Self-reactive Substances: Regardless of PG, follow the specific packaging rules
- Class 6.2 Infectious Substances, Category A: Regardless of PG, use PI 620-specific packaging
- Class 7 (Radioactive Materials): Separate Type A / Type B container systems
All other Classes 3 / 4 (certain subclasses) / 5.1 / 6.1 / 8 / 9 follow PG I/II/III.
III. How to Read UN Packaging Codes: The Meaning of the 6-Segment Code
This is the most valuable “code-reading skill” on the front lines of air cargo DG packaging.
Here’s a random example of an actual format:
`` UN 4G/Y15/S/24/D/BAM-12345 ``
Break it down into 6 segments:
| Segment | Character | Meaning |
|---|
| 1 | UN | The "This is UN-compliant packaging" label |
| 2 | 4G | Packaging type code (4 = box, G = fiberboard box) |
| 3 | Y15 | Packaging grade + maximum gross weight (kg). Y = PG II/III General Purpose, 15 = maximum 15 kg |
| 4 | S | Type of contents (S = solid or inner packaging; for liquids, the specific gravity is indicated, e.g., 1.4） |
| 5 | 24 | Year of manufacture (last two digits, e.g., 2024) |
| 6 | D | Country code of manufacture (D = Germany) |
| 7 | BAM-12345 | Certifying Authority + Packaging Manufacturer Number |
Common combinations for "Packaging Type Code" in Paragraph 2
| Code | Type |
|---|
| 1A1 / 1A2 | Steel drum (closed-top / open-top) |
| 1H1 / 1H2 | Plastic drums (closed-top / open-top) |
| 3H1 / 3H2 | Plastic cans |
| 4G | Fiberboard boxes (the most common type of cardboard box) |
| 4GV | Multi-purpose fiberboard box (with additional internal cushioning) |
| 4H2 | Solid plastic box |
| 6HA1 / 6HG1, etc. | Combined Packaging |
| 1G | Fiberboard drums |
| IBC (31HA1, etc.) | Intermediate Bulk Containers |
The most commonly used packaging for cross-border e-commerce are 4G (standard cardboard boxes) and 4GV (multi-purpose cardboard boxes with cushioning). Most Class 3 liquids shipped by air consist of a combination of 4G packaging, an inner plastic bottle, and absorbent material.
How to interpret “Packaging Class + Maximum Quantity” in Paragraph 3
- Letters: X / Y / Z = PG I / II / III
- Numbers:
- Solids or inner packaging: Maximum gross weight (kg)
- Liquids: Maximum specific gravity (upper limit of liquid density)
If your cargo is a liquid, Paragraph 4 will specify the measured pressure (e.g., 100 indicating 100 kPa); if the shipment is a solid or inner packaging, Paragraph 4 will state S。
IV. Internal Structure of the PI: What Each PI Covers
If you open any PI in Chapter 5 of the DGR, the structure is generally as follows:
- Additional Requirements (conditions added for special scenarios)
- Maximum Quantity on Passenger Aircraft / Maximum Quantity on All-Cargo Aircraft (repeating the weight limits from the DGL table)
- List of Permitted Single Packages (if the PI allows single packages)
- List of Permitted Combined Packages (inner packaging + outer packaging + maximum per-piece limit)
- Special Packaging Requirements (e.g., “Inner packagings must be separated by absorbent material,” “Directional labels are required”)
Here’s a specific example—PI 353 (Passenger Aircraft, Class 3 PG II Liquids):
| Requirements | Details |
|---|
| Maximum Single-Piece Limit for Passenger Aircraft | 5 L (aggregate value) |
| Single packaging allowed | Generally not permitted (must be packed in combination) |
| Permitted combined packaging | Glass / plastic / metal inner bottles + 4G cardboard boxes / 4H2 plastic crates, etc., as outer packaging |
| Inner container limits | Glass ≤ 1 L, plastic ≤ 5 L, metal ≤ 5 L |
| Packaging Grade Requirements | Outer packaging must be at least Y (PG II) |
| Required labels | Main Class Label: Class 3, Directional Arrow |
The PI isn’t a mystery—it’s simply a “combination menu” of “inner container + outer packaging + volume limits + required labels.” Review it three times and you’ll get the hang of it.
V. Single Packaging / Combination Packaging / IBC / Overpack: Four Forms
| Form | Meaning | Typical Real-World Scenarios |
|---|
| Single Packaging | Contents are packed in a single UN-compliant container, with the container itself serving as the outer packaging | Lubricating oil in steel drums, alkaline solution in IBCs |
| Combination Packaging | Multiple inner packages (bottles/cans) + 1 outer carton | Most common in cross-border e-commerce: glass bottles + 4G cardboard boxes |
| IBC (Intermediate Bulk Container) | Intermediate Bulk Container, typically ≥1 m³ | Industrial chemicals, large-volume liquids |
| Overpack | Multiple compliant packages consolidated into a single outer container (pallet + stretch wrap / large box) | Less-than-container load (LCL) and full-pallet shipments |
Overpacking is prone to pitfalls. The rules do not simply require wrapping multiple boxes together; rather:
- The outer packaging must clearly display all inner dangerous goods labels (either visible through the packaging or reproduced and affixed to the outer layer)
- The outer packaging must be marked with the word “OVERPACK”
- Each inner package must already be compliant on its own
VI. Performance Testing: What DGR Chapter 6 Tests
UN-compliant packaging must pass a set of “penetration” tests before being released to the market. Frontline staff do not need to know how to perform these tests, but they must be able to review test reports to determine whether a particular packaging design is compliant:
| Test | Purpose | Passes Core Standards |
|---|
| Drop Test | Simulates impacts during handling | No leakage of contents is permitted (PG I/II tests are conducted at higher heights) |
| Stack Test | Simulates 24-hour warehouse stacking | Must not deform or rupture under the weight of the upper layer |
| Hydraulic Pressure Test | For liquids only; tests the inner bottle’s pressure resistance | Typically 100 kPa or higher; must be leak-free |
| Leakproofness Test | For single-use liquid packaging only | Must not leak when submerged under air pressure |
The packaging manufacturer provides a UN Test Report upon shipment. When selecting a product, we recommend requesting this report from your supplier to verify the following:
- The packaging type code matches the second digit of your UN specification code
- The packaging test grade (X/Y/Z) meets your PG requirements
- The specific gravity of the test contents is close to your actual specific gravity (for liquids)
- The test date falls within a reasonable timeframe (certain items generally require retesting every 12 months)
VII. 4G vs. 4GV vs. 4H2: How to Choose Among the Three Main Types of Outer Packaging
For DG shipments in cross-border e-commerce and industrial exports, 80% use one of these three outer packaging types: 4G, 4GV, and 4H2. While they all appear to be “boxes,” they differ significantly in terms of Proforma Invoice (PI) compatibility, price, and strength.
| Type | Full Name | Material | Strength Characteristics | Price Range | Typical Applications |
|---|
| 4G | Fiberboard Boxes | Multi-layer corrugated cardboard | Standard | Minimum | General PG II/III liquids, small batches |
| 4GV | Multi-purpose fiberboard boxes | Corrugated cardboard + built-in cushioning material | Highly versatile (one certification allows for multiple inner bottles) | Medium | Multi-SKU mixed shipments, small e-commerce items |
| 4H2 | Solid-core plastic box | Injection-molded high-density plastic | Moisture-resistant, chemical-resistant | High | High-humidity environments and scenarios with highly corrosive chemicals |
Practical Selection Guidelines:
- Single, stable SKU + price-sensitive → 4G. However, changing the inner bottle specification requires technically re-matching the UN Test Report each time.
- Multiple SKUs in mixed loads, with frequent changes to inner bottle specifications → 4GV. Its certification allows for flexible combinations of inner bottles within a certain range, eliminating the hassle of re-matching each time.
- Destinations with high humidity or prone to water splashes (LCL shipments, Southeast Asia/South America routes) → 4H2. The extra cost ensures the container won’t warp or leak.
The Hidden Value of 4GV: Many e-commerce sellers are unaware that the scope of 4GV certification is much broader than that of 4G. A single 4GV certification can cover multiple capacity combinations of glass, plastic, and metal bottles, as long as they comply with the “Permitted Combinations Table” in the certification documents.One purchase covers multiple products, making it more cost-effective than 4G in the long run.
Typical Selection Scenario Comparison:
- Product Selection: 100ml perfume (PG II liquid) × 24 bottles/case × 200 cases shipped monthly → Select 4GV/Y15/S (one certification covers multiple SKUs)
- Product: Single SKU 1L alcohol-based hand sanitizer (PG II liquid) × 12 bottles/case × 50 cases shipped monthly → Select 4G/Y20/S (most cost-effective)
- Product Selection: 500g industrial solid oxidizer (PG II Solid) × LCL shipment → Select 4H2/Y30/S (moisture protection)
- Product Selection: Single batch of 500 bottles of workshop paint thinner (PG III liquid) shipped as oversized cargo → Consider IBCs instead of combination packaging
Purchasing Pitfalls: When buying UN-compliant containers, require the supplier to specify in the contract that “a copy of the UN Test Report is attached” and that “the UN code printed on the container matches the one in the report.” Some suppliers may try to pass off “containers bearing the UN mark” as genuine, even though they lack full certification. If the seal is torn off later, you’ll have no evidence to protect your rights.
VIII. How to Read a UN Test Report: 3-Minute Checklist
When a supplier provides you with a UN Test Report (usually in English plus the language of the certifying country), it may look like a jumble of charts and data, but you actually only need to verify these few lines:
| Items to Verify | Typical Location in the Report | What to Look For |
|---|
| Packaging Type Code | Report Header | 4G / 4GV / 4H2, etc.—must match the code printed on the outer carton |
| Packing Group Tested | Header or Test Conditions | X / Y / Z; must be ≥ the PG of your cargo |
| Inner Packaging Combinations | Middle Table | List of permitted inner bottle size combinations; your inner bottles must fit within these |
| Maximum Gross Mass | Test Conditions | Maximum Gross Mass per Outer Carton |
| Specific Gravity | Liquid Test Conditions | The specific gravity of the test liquid must be ≥ your actual specific gravity |
| Test Results | Final | Drop / Stack / Hydraulic / Leakproofness: All “PASS” |
| Certificate Issuance Date | Header or Footer | Certificates issued within the last year are current; for those issued more than two years ago, verify whether they are still valid |
| Issuing Authority | Stamp at the bottom | BAM (DE) / DOT (US) / CAA (UK), etc., recognized by the destination country |
The most common pitfall is “Inner Packaging Combinations.” If you purchase a 4GV/Y20/S outer carton but the inner bottles you pack do not fall within its certified combination range—technically, this is equivalent to having no certification. If ground handling staff spot this during a random inspection, the entire shipment will be rejected.
For cross-border e-commerce sellers shipping directly from factories, it is recommended that the factory provide a backup copy of the corresponding UN Test Report for each SKU. Keep these records on file for at least 3 years to prepare for customs traceability audits.
IX. Absorbent Materials / Cushioning Materials: The Hidden Threat in Liquid DG Packaging
Liquid PIs such as PI 353 and PI 364 both contain an easily overlooked requirement: “When the total volume exceeds X L, absorbent material sufficient to absorb all contents must be provided.”
There are three common types of absorbent materials:
- Mineral powders such as vermiculite and diatomaceous earth
- Chemical absorbent pads (select oil-absorbent or water-absorbent types as appropriate)
- Specialized leak-proof bags
The most common mistake made by beginners:
- Using ordinary newspaper or foam as absorbent material → Fails to meet standards
- Insufficient amount of absorbent material; theoretically, a leak from just one bottle would spill outside the packaging → Does not meet standards
- Chemical reaction between the absorbent material and the liquid (e.g., absorbent material coming into contact with a strong oxidizing agent) → Hazardous
Correct Procedure: Prepare absorbent material equal to 1.0 times the maximum volume of the inner bottle (or 1.2 times for a more conservative approach), and verify chemical compatibility with the cargo.
10. Limited Quantity (PI with “Y” prefix): A “Semi-Exemption” Shortcut
If a row in the DGL table has a value in the “Ltd Qty PI” column, such as Y341, this indicates that if this shipment is packed according to the limited quantity rules, it can follow a simplified process.
Benefits of using the Limited Quantity procedure:
- Lower packaging strength requirements (generally, Class Y cartons are sufficient)
- No full DGD required (some destination countries still require a simplified declaration)
- Outer cartons must be marked with a special “Y” symbol (a diamond shape filled with black at the top and bottom; a horizontal line may be drawn across the top and bottom points, leaving the center blank; dimensions must be at least 100×100 mm)
However, please note:
- Both the single unit and the inner bottle must be below the limit threshold
- Applies only to certain Classes and PG categories
- The Y-limit thresholds differ for passenger aircraft and all-cargo aircraft; refer to the corresponding column in the DGL
- Not all UN numbers are permitted to be shipped as “Limited Quantity”; check the relevant column in the DGL to see if a value is listed
For cross-border e-commerce businesses whose product selection focuses on small-volume liquids (such as 50ml perfumes or 100ml alcohol-based hand sanitizers), shipping under the “Limited Quantity” allowance is a very cost-effective option, but quantities must be strictly controlled.
If you need to quickly determine whether a shipment qualifies for Limited Quantity and how to apply the label, you can use OneCargoKit’s Cargo Label Generator to directly generate templates with the corresponding “Y” mark and directional arrows. Combined with the Packing Size Advisor, you can calculate the optimal number of inner bottles to pack in an outer box.
XI. Common Misconceptions
- Misconception 1: If a cardboard box appears to have “UN” on it, it’s compliant — Wrong. The UN marking must consist of all 6 segments; if even one segment is missing, it’s invalid.
- Misconception 2: “Y” is a universal marking for any carton — Wrong. Y = PG II/III; it must never be used for PG I.
- Misconception 3: As long as the outer carton of a combination package is compliant, any mineral water bottle can be used as the inner container —— Wrong. The inner container must also meet the requirements specified in the PI regarding material, capacity, and whether a specific threaded seal is required.
- Misconception 4: Placing multiple bottles of liquid in a large plastic bag and then placing that inside the outer packaging counts as “absorption” —— Wrong. Absorbent materials have specific chemical requirements; plastic bags do not qualify as absorbent materials.
- Misconception 5: Directional arrows are not required for limited-quantity shipments —— Wrong. All packages containing liquid dangerous goods, regardless of whether they are limited-quantity shipments, must be labeled with directional arrows.
- Misconception 6: Packaging can still be used even if it’s past its expiration date — UN packaging generally has a service life from the date of manufacture that must be assessed according to the manufacturer’s specifications and DGR requirements. Special attention must be paid to the aging of plastic containers.
- Misconception 7: The “OVERPACK” label is optional because it’s obvious anyway — Wrong. Regulations explicitly require the outer packaging to be marked with “OVERPACK” plus the total number of items inside and the total gross weight.
- Misconception 8: There is no need to verify the pressure rating when packing liquid dangerous goods in IBCs —— Wrong. IBCs must also comply with the maximum allowable capacity and pressure rating specified in the PIF, and are subject to periodic re-inspection requirements.
XII. Practical Checklist: Packaging Verification—90-Second Walkthrough
- [ ] DGL line is locked, PG has been confirmed
- [ ] PI number matches Passenger / Cargo
- [ ] The outer packaging displays the complete 6-segment UN regulation marking, and the class (X/Y/Z) meets or exceeds PG requirements
- [ ] Year, country, and manufacturer’s number clearly visible on the outer packaging
- [ ] Inner bottle material and capacity comply with the PI’s approved list
- [ ] Inner container sealing method complies with PI (some require threaded caps with gaskets)
- [ ] Sufficient absorbent material has been provided for the liquid, and chemical compatibility has been verified
- [ ] There is sufficient cushioning between inner bottles (to prevent impact)
- [ ] Total weight per package does not exceed the PI Passenger/Cargo weight limit
- [ ] Main class label, subsidiary class label, handling label, and directional arrow are all present
- [ ] Quantity-limited goods have been marked with a “Y” label
- [ ] The overpack is labeled with “OVERPACK,” the number of packages, and the total gross weight
- [ ] The UN Test Report provided by the manufacturer has been filed
13. Classification Methods for the Three Categories
| Position | Key Steps in Packaging Decision-Making | Output |
|---|
| Freight Forwarder Operations | Verify UN code during inspection + cross-reference with DGL PG | Whether to accept or return for repackaging |
| Cross-Border E-Commerce Operations | When selecting products, calculate the volume per item to determine if it meets the volume limit | Whether to list the product and the packaging solution for each SKU |
| Factory / Supplier | Procure UN-compliant packaging + request a UN Test Report | Packaging Compliance Before Shipment |
When planning packaging for cross-border e-commerce, you also need to do a cost-benefit analysis: which option results in the lowest volumetric weight and billable weight—using a 4G/Y20/S box to pack 24 bottles of 100ml, or using a 4GV/Y15/S box to pack 20 bottles of 100ml?Run the calculation through the Chargeable Weight Calculator to get the answer quickly.
XIV. Compliance and Boundary Reminders
- This article is a practical guide based on the publicly available IATA DGR packaging system and does not constitute legal, compliance, or safety advice
- Specific performance testing methods and re-inspection cycles for UN-compliant packaging are subject to the current edition of Chapter 6 of the IATA DGR.
- Certifying authorities for UN-compliant packaging vary by country (e.g., BAM in Germany, DOT in the U.S., CAA in the U.K.). When sourcing packaging across borders, ensure that the certificates are recognized in both the destination country and any transit countries.
- Packaging for categories such as lithium batteries, infectious substances, and radioactive materials follows specific PI codes (e.g., PI 965–970, PI 620, and PI 950 series). These are not covered in this article and require separate, in-depth study.
- It is strongly recommended to source packaging from qualified manufacturers and to retain the UN Test Report for each batch
XV. Conclusion: Packaging compliance is the “most cost-effective compliance investment” in the DG supply chain
Many people think UN-compliant packaging is expensive and try to cut costs wherever possible. But when you do the math, you’ll find the opposite is true:
- A 4G Y-corrugated carton costs a few yuan more than a standard carton, but a single instance of non-compliant packaging can result in the entire shipment being refused for transport, rerouted, returned at the destination port, and requiring compensation to the customer.
- A UN Test Report costs virtually nothing (it’s provided by the factory upon shipment), but failing to produce it during a spot check will be deemed a misdeclaration
- Properly configuring absorbent materials ensures that a single 1-liter bottle of liquid breaking won’t affect the entire carton, preventing on-the-spot refusal by ground handling staff and the need for cleanup of ground contamination
Packaging is the lowest-cost, highest-return link in the entire DG supply chain. At the same time, it is the link most easily overlooked by non-experts (purchasing staff, suppliers, and new operators). Manage this link effectively, and your DG shipment incident rate will drop by an order of magnitude.
In the next post, we’ll continue exploring the “compliance chain”: how to properly apply labels, markings, and directional arrows; the mandatory rules regarding label placement, size, and color; and the most common labeling errors that lead to rejection during ground handling spot checks. See you next time.