- Each IMDG class has different packaging group assignments and testing requirements under the 危包证 system.
- Class 2 (gases) uses cylinder-specific rules. Class 3 (flammable liquids): UN-rated steel/plastic drums are standard.
- Class 9 (miscellaneous, including lithium batteries) is the most common for China DG exports and has the highest volume of 危包证 applications.
- Packaging must bear UN mark with manufacturer code, UN number, packing group, and year of manufacture.
IMDG class and packaging group overview
The IMDG Code divides dangerous goods into 9 classes. According to the International Maritime Organization (IMO), the current IMDG Code Amendment 42-24 contains over 3,500 individual dangerous goods entries with specific packaging instructions for each class and packing group. Classes 1 (explosives) and 7 (radioactive materials) have specialized packaging regimes outside the standard 危包证 process. Classes 2, 3, 4, 5, 6, 8, and 9 use the UN performance packaging system that the 危包证 certifies.
Within most classes, substances are further assigned a packing group (PG I, II, or III) based on the degree of danger: PG I = high danger, PG II = medium danger, PG III = low danger. The packing group determines the severity of UN performance tests the packaging must pass. For example, a drop test height is 1.8m for PG II but only 0.8m for PG III.
| IMDG Class | Name | Packing Groups | Common Chinese Export Products |
|---|---|---|---|
| Class 2 | Gases | N/A (cylinder rules) | Aerosols (UN1950), refrigerants, compressed air |
| Class 3 | Flammable liquids | I, II, III | Paints, adhesives, solvents, alcohol-based products |
| Class 4 | Flammable solids | I, II, III (varies by division) | Metal powders, sulfur, matches, calcium carbide |
| Class 5 | Oxidizing substances & organic peroxides | I, II, III (varies by division) | Hydrogen peroxide, ammonium nitrate fertilizers |
| Class 6 | Toxic & infectious substances | I, II, III (toxic only) | Pesticides, industrial chemicals, disinfectants |
| Class 8 | Corrosives | I, II, III | Sulfuric acid, sodium hydroxide, cleaning chemicals |
| Class 9 | Miscellaneous DG | None (but PG II test standard applies) | Lithium batteries (UN3480/UN3481), BESS (UN3536), environmentally hazardous substances (UN3077/UN3082) |
Class 2 (gases): cylinder and pressure vessel packaging
Class 2 is the exception to the standard UN packaging system. Gases are transported in pressure receptacles (cylinders, tubes, pressure drums, and cryogenic containers), not drums or boxes. The 危包证 process for Class 2 focuses on the pressure vessel rather than standard UN packaging.
Packaging requirements for Class 2
- Pressure receptacles must meet GB standards (e.g., GB 5100 for welded steel cylinders, GB 5842 for LPG cylinders). The manufacturer must hold a Special Equipment Manufacturing License (特种设备制造许可证) from China's SAMR.
- Periodic inspection certificates are required. In China, gas cylinders must be re-inspected every 2-3 years depending on gas type. The inspection certificate is separate from the 危包证 but is required as supporting documentation.
- Valve protection caps must be in place and secured. Cylinder valves are the most vulnerable point during transport.
- Aerosol dispensers (UN1950) are the most common Class 2 export from China. These are tested under a different protocol: hot water bath test at 55 degrees C. Capacity limits: 1L for metal, 500ml for glass/plastic.
In Qingdao, most Class 2 exports are aerosol products (personal care, household cleaners) and refrigerant gases. The MSA treats Class 2.1 (flammable gases) with strict stowage requirements: on-deck stowage only, away from heat sources.
Class 3 (flammable liquids): UN-rated drums and jerricans
Class 3 is one of the highest-volume DG categories for China exports and one of the most straightforward for 危包证. The key variable is the flash point, which determines the packing group.
Packing groups for Class 3
| Packing Group | Flash point (closed cup) | Initial boiling point | Drop test height |
|---|---|---|---|
| PG I | - | 35 degrees C or below | 1.8m |
| PG II | Below 23 degrees C | Above 35 degrees C | 1.2m |
| PG III | 23-60 degrees C (inclusive) | Above 35 degrees C | 0.8m |
Typical packaging for Class 3 from China
- Steel drums (1A1): 20L to 200L. Most common for industrial solvents, paints, and adhesives. Must include internal coating if product is corrosive to steel.
- Plastic jerrycans (1H1): 5L to 25L. Common for smaller-volume chemical exports. PG II jerrycans must pass a 1.2m drop test.
- Composite packaging (6HA1): plastic inner container with steel outer. Used for high-purity solvents where metal contact is prohibited.
- Ullage (headspace) requirement: liquids must leave minimum 5% empty space at 55 degrees C fill temperature to allow for thermal expansion. This is checked during the on-site Customs inspection for the Use Appraisal Certificate.
For shippers in Shandong exporting Class 3 products, our DG team in Qingdao handles everything from matching your product's packing group to the correct packaging specification through full 危包证 processing. See the application process guide for step-by-step details.
Class 4 (flammable solids): fiberboard boxes, bags, and special provisions
Class 4 has three divisions, each with distinct packaging requirements:
- Class 4.1 (flammable solids): sulfur, metal powders (aluminum, magnesium), naphthalene. Standard UN packaging in boxes, drums, or bags. PG II is most common. Metal powders require airtight packaging to prevent moisture contact.
- Class 4.2 (spontaneously combustible): white/yellow phosphorus, activated carbon. Requires airtight, nitrogen-filled or hermetically sealed packaging. Often double-packaged with inner glass ampoules inside metal cans inside outer fiberboard boxes.
- Class 4.3 (dangerous when wet): calcium carbide, sodium metal. Must be packed in hermetically sealed containers. Water-tight packaging is critical. Calcium carbide exports from China typically use steel drums with airtight closures.
Key packaging rules for Class 4
- Class 4.2 and 4.3 substances generally cannot use plastic outer packaging alone, plastic deformation under heat can compromise the seal.
- Calcium carbide (UN1402) must be packed in hermetically sealed steel drums (1A1) with gasketed closures. The acetylene gas produced by contact with water is highly flammable.
- For Class 4.1 solids in fiberboard boxes (4G), the box must pass the stacking test at PG II level regardless of the substance's assigned packing group.
Class 5 (oxidizing substances and organic peroxides): inner packaging rules
Class 5 has two distinct divisions with very different packaging approaches:
Class 5.1 (oxidizing substances)
Standard UN packaging applies. Common Chinese exports: hydrogen peroxide solutions, ammonium nitrate fertilizers, potassium permanganate. The packaging material must be chemically compatible, oxidizers can react with certain plastics and organic materials. Plastic packaging for 5.1 substances must be tested for chemical compatibility.
Class 5.2 (organic peroxides)
These are among the most tightly regulated DG for packaging. Organic peroxides can decompose exothermically and some require temperature control during transport. Key packaging requirements:
- Maximum quantity per package is strictly limited (varies by specific organic peroxide, defined in IMDG Code 2.5.3.2.4).
- Packaging must include a venting or pressure relief mechanism unless the specific organic peroxide is exempted.
- Temperature-controlled organic peroxides require insulated or refrigerated packaging with temperature monitoring.
- Organic peroxides requiring temperature control are among the few DG categories that cannot use the standard 危包证 process alone. The temperature control plan must be separately approved.
Class 6 (toxic and infectious substances): double-layer requirements
Class 6.1 (toxic substances)
Standard UN packaging applies but with stricter closure and contamination prevention requirements. PG I toxic substances (oral LD50 below 5 mg/kg) have the most stringent packaging rules: maximum 400kg gross mass for steel drums, zero tolerance for any leakage during testing.
For liquids, packaging must have a secondary containment or absorbent material capable of absorbing the entire liquid contents in case of primary container failure. This is verified during the leakproofness test.
Class 6.2 (infectious substances)
These are rare in general DG exports. Category A infectious substances (UN2814, UN2900) require triple packaging: leakproof primary receptacle, leakproof secondary packaging, and rigid outer packaging. All three layers must maintain integrity even if the package is dropped. Category B substances (UN3373) follow the IATA PI650 standard, which is similar but less demanding.
Class 8 (corrosives): material compatibility and inner coating
Class 8 is material-compatibility driven. The packaging must resist chemical attack from the contents for the entire transport duration, including any potential leakage scenarios.
Material selection by corrosive type
| Substance type | Recommended packaging material | Materials to avoid | Typical packaging code |
|---|---|---|---|
| Strong acids (sulfuric, hydrochloric, nitric) | HDPE plastic, glass inner + plastic outer | Steel (rapid corrosion), aluminum | 1H1, 6HA1 (plastic inner/steel outer with coating) |
| Strong alkalis (sodium hydroxide, potassium hydroxide) | HDPE plastic, steel with corrosion-resistant coating | Aluminum (reacts), uncoated steel | 1H1, 1A1 with inner coating |
| Oxidizing acids (nitric acid) | Stainless steel, glass inner only | Plastic (degradation), carbon steel | Specialized, case-by-case |
Inner coating requirement: If steel drums are used for corrosives, an internal epoxy or phenolic coating is mandatory. The Performance Certificate must specifically note the coating type. Uncoated steel drums are rejected for corrosive liquids.
In Shandong, Class 8 exports include industrial cleaning chemicals, battery electrolyte, and chemical intermediates. Qingdao Port's DG terminal handles Class 8 cargo in a dedicated area with spill containment systems.
Class 9 (miscellaneous DG including lithium batteries): special focus
Class 9 is the fastest-growing DG category from China and the most important for 危包证 because of the volume of lithium battery exports. According to the China Port and Harbor Association, Class 9 DG declarations at major Chinese ports increased by over 60% year-over-year in 2025, driven almost entirely by lithium battery and BESS exports. It covers three main product groups:
Lithium batteries (UN3480, UN3481, UN3536)
This is the number one product category for Class 9 危包证 applications. According to the International Maritime Organization (IMO), lithium battery-related DG entries have been among the most frequently updated sections of the IMDG Code, reflecting the rapid evolution of battery technology and transport safety science. Key rules:
- UN38.3 test report is mandatory before 危包证. This is a prerequisite. The 危包证 application will not be accepted without a valid UN38.3 test report from an accredited laboratory. See our lithium battery 危包证 guide for full details.
- UN3480 (standalone batteries): requires UN-spec fiberboard boxes (4G) or approved equivalent. Cells at 30% SOC or below. Inner packaging must prevent short circuits: each battery must be in a non-conductive inner bag or separated by non-conductive dividers.
- UN3481 (batteries with/contained in equipment): equipment provides primary protection. Outer packaging must still be rigid and strong enough for transport.
- UN3536 (BESS in cargo transport units): the container itself is the packaging. The 危包证 process involves container structural certification rather than traditional packaging testing. See our UN3536 guide for the full documentation chain.
Environmentally hazardous substances (UN3077, UN3082)
UN3077 (solid) and UN3082 (liquid) are environmentally hazardous substances that present a hazard to the aquatic environment. They are the most common non-battery Class 9 exports from China. The 2025 Differentiated Assessment system treats these as low-risk, often qualifying for document-only verification of the 危包证. Standard UN packaging applies at PG III test level.
Other Class 9 entries
- UN3363 (DG in apparatus/machinery): applies to equipment containing small quantities of various DG. Packaging is typically the equipment's own casing with additional protection.
- UN3508 (capacitors, asymmetric): special rules apply. These can be shipped as non-DG under certain conditions.
Quick reference table: packaging type by class and packing group
| IMDG Class | Common UN Numbers | Typical Packaging Codes | Packing Group | Special Notes |
|---|---|---|---|---|
| 2.1 (Flammable gas) | UN1950 (aerosols), UN1011 (butane) | Cylinder specs per GB 5100 | N/A | Periodic inspection req'd |
| 2.2 (Non-flammable gas) | UN1066 (nitrogen), UN1002 (air) | Cylinder specs per GB 5099 | N/A | Green label on cylinder shoulder |
| 3 (Flammable liquid) | UN1263 (paint), UN1170 (ethanol) | 1A1, 1H1, 3H1, 6HA1 | I, II, or III | Ullage 5% min at 55C fill temp |
| 4.1 (Flammable solid) | UN1325, UN1350 (sulfur) | 4G, 5H3, 1A2 | II or III | Metal powders: airtight req'd |
| 4.2 (Spontaneously combustible) | UN1361 (carbon) | 1A1 hermetically sealed | I or II | Nitrogen-filled often req'd |
| 4.3 (Dangerous when wet) | UN1402 (calcium carbide) | 1A1 hermetically sealed | I or II | Water-tight, gasketed closures |
| 5.1 (Oxidizer) | UN1490 (potassium permanganate) | 1A1, 1H1, 4G | I, II, or III | Material compatibility critical |
| 5.2 (Organic peroxide) | UN3105 (various) | Case-by-case; vented packaging may be required | II | Temperature control may apply |
| 6.1 (Toxic) | UN2811 (toxic solid, organic) | 1A1, 1H1, 4G | I, II, or III | PG I: max 400kg per package |
| 8 (Corrosive) | UN1830 (sulfuric acid) | 1H1, 1A1 with inner coating | I, II, or III | Material compatibility mandatory |
| 9 (Misc DG) | UN3480 (Li-ion batteries), UN3077 (env. hazardous) | 4G, 1A1, CTU (UN3536) | PG II test level | UN38.3 for Li-ion; 2025 differentiated assessment for UN3077/UN3082 |
10. Frequently asked questions
Can the same packaging be used for multiple DG classes?
Only if the packaging has been tested and certified for all those classes, and the Performance Certificate explicitly lists them. Most UN-certified packaging is approved for a range of DG classes and packing groups, listed on the certificate. Check the certificate before assuming a packaging type is suitable for your specific product.
What happens if I use the wrong packing group for my DG class?
The Use Appraisal Certificate application will be rejected during document review. The reviewing Customs officer cross-references the packing group on your DG Classification Report against the packaging's approved packing groups on the Performance Certificate. A mismatch is an automatic fail. You must use packaging tested at or above the packing group level of your substance.
Do Class 9 lithium batteries need the same drop test as Class 3 flammable liquids?
Yes. Class 9 packaging is tested at the PG II performance level, which means a drop test from 1.2m. The same 1.2m drop test applies whether you are shipping Class 3 PG II paint or Class 9 UN3480 lithium batteries in fiberboard boxes. The test procedure is the same, the substance inside the packaging is what differs.
How do I know which packaging code to put on my Single Window application?
The packaging code appears on the Performance Certificate from your packaging manufacturer. It will be something like "1H1/Y1.5/250/22/CN/C39001". The first three characters (e.g., "1H1") are the UN packaging type code. Enter exactly this code in your Use Appraisal application. The Single Window system validates it against the Performance Certificate database.
Not sure which packaging type your product needs?
Our DG team matches your product to the correct UN packaging specification and manages the full 危包证 process. From DG classification review through Certified packaging sourcing to Customs inspection and MSA declaration.
Ask Our DG Team → Pillar Guide →DG Packaging Certificate: Complete Guide Series
Explore all guides in this cluster:
Complete overview, two certificates, costs, 2025 rules.
Step-by-step, Single Window, rejection reasons.
UN38.3, SP188, air vs sea, 2025 EV codes.
Also see: UN3536 Energy Storage Guide →
Sources and references
- 《中华人民共和国进出口商品检验法》第17条: Legal basis for mandatory DG packaging inspection. 全国人民代表大会.
- SN/T 0370-2021: 出口危险货物包装检验规程 (China DG packaging inspection standards). Issued by GACC (海关总署).
- China International Trade Single Window (中国国际贸易单一窗口): Online application portal for DG packaging certificates. singlewindow.cn
- Differentiated Conformity Assessment (差异化合格评定): GACC announcement 2025年第8期, UN3077/UN3082 Class 9 streamlined procedure. 中国海关 2025年08期
- 危包证有效期: 空运3个月, 海运/陆运/铁路12个月: per CIQ inspection standards. ChemRadar Regulatory
- UN38.3 Test Report requirement: UN Manual of Tests and Criteria, Part III, Section 38.3. Mandatory for lithium battery DG shipments from Chinese ports.
- Ningbo Port mandatory UN38.3 effective October 2025: ONE Advisory Oct 2025
All procedural descriptions verified against GACC published guidelines and Great Hensen operational experience. Last verified: July 2026.