IMDG Class 2 covers gases — substances that are gaseous at 20°C at standard pressure, or that are transported as compressed, liquefied, dissolved, or refrigerated liquefied gas. Class 2 shipments from China require specific UN-certified pressure receptacles, advance carrier DG booking, and compliance with both IMDG and Chinese port regulations. This guide covers everything China-based exporters need to know to ship Class 2 gases safely and compliantly.
Class 2 Sub-Divisions
The IMDG Code divides Class 2 into three sub-divisions, each with different hazard profiles, packaging requirements, and carrier acceptance rules:
2.1 — Flammable Gases
Gases that ignite when mixed with air in concentrations of 13% or less, or have a flammable range of at least 12 percentage points. These pose the highest fire risk among Class 2 gases and require fire-isolated stowage on vessels.
- Propane (UN1978) — used in heating, cooking, and as an industrial fuel
- Butane (UN1011) — lighter fuel, aerosol propellant
- Acetylene (UN1001) — welding and metal cutting
- Hydrogen (UN1049) — industrial processing, fuel cells
- Methane (UN1971) — natural gas, chemical feedstock
- Ethylene (UN1962) — polymer production, fruit ripening
2.2 — Non-Flammable, Non-Toxic Gases
Gases that are neither flammable nor toxic but may cause asphyxiation by displacing oxygen, or act as oxidizers supporting combustion. Generally the easiest DG class to ship by sea.
- Nitrogen (UN1066) — industrial blanketing, food packaging, electronics manufacturing
- Oxygen (UN1072) — medical, welding, industrial oxidation
- Helium (UN1046) — cryogenics, leak detection, balloons
- Carbon dioxide (UN1013) — beverages, fire extinguishers, refrigeration
- Compressed air (UN1002) — diving, industrial pneumatics
- Argon (UN1006) — welding shielding gas, lighting
- Refrigerant gases (UN1078/UN3159) — HVAC and refrigeration systems
2.3 — Toxic Gases
Gases that are toxic or corrosive to humans, posing a health hazard. Class 2.3 is the most restricted sub-division with limited carrier acceptance and more stringent documentation requirements.
- Chlorine (UN1017) — water treatment, chemical manufacturing
- Ammonia, anhydrous (UN1005) — fertilizer production, refrigeration
- Sulfur dioxide (UN1079) — food preservative, chemical intermediate
- Hydrogen sulfide (UN1053) — industrial chemical processing
- Carbon monoxide (UN1016) — chemical synthesis
Aerosol products (UN1950): Aerosols are a special case within Class 2. They can be assigned to 2.1 or 2.2 depending on propellant flammability, but are shipped under a single UN1950 classification with specific provisions about heat resistance and burst pressure. Consumer aerosol products (deodorants, spray paints, insecticide sprays, cleaning sprays) commonly ship as UN1950 from Chinese factories.
Packaging Requirements for Class 2 Gases
Class 2 gas packaging is governed by Chapter 6.2 of the IMDG Code for pressure receptacles. The following requirements are mandatory for all Class 2 exports from China:
- UN-certified pressure receptacles: Cylinders must be constructed to UN standards (ISO 9809 or equivalent) with valid periodic inspection and test (hydrostatic pressure test) certificates — typically valid for 5 or 10 years depending on gas type.
- Valve protection: Valves must be protected by caps, shrouds, or collars that can withstand impact. For toxic gases (2.3), valve outlets must be plugged or capped.
- Leak testing: Each cylinder must undergo a leak-proofness test before filling and before shipment. Test records must be retained.
- Fill ratio compliance: Cylinders must not be filled beyond their rated fill ratio (kg of gas per liter of water capacity) at 65°C reference temperature.
- Labeling: Each cylinder must carry the Class 2 hazard label, the appropriate sub-division label (flammable/non-flammable/toxic), and the correct UN number.
- Aerosols (UN1950): Must withstand 55°C without bursting or leaking. Inner receptacles typically limited to 1,000 mL capacity. Outer packaging must be strong enough to prevent accidental discharge. Water bath testing is standard for aerosol production quality control.
Carrier DG Acceptance Policy for Class 2
Not all carriers treat Class 2 the same. The table below reflects current (2026) acceptance policies for sea freight from China. Policies can change based on vessel configuration, route, and seasonality:
| Carrier | Class 2.1 (Flammable) | Class 2.2 (Non-Flammable) | Class 2.3 (Toxic) | UN1950 (Aerosols) |
|---|---|---|---|---|
| MSK | Accepted (advance booking) | Accepted | Restricted (route-dependent) | Accepted |
| HPL | Accepted (advance booking) | Accepted | Not accepted | Accepted |
| MSC | Accepted | Accepted | Limited acceptance | Accepted |
| COSCO | Accepted (advance booking) | Accepted | Case-by-case | Accepted |
| HMM | Accepted | Accepted | Not accepted | Accepted |
| OOCL | Accepted (advance booking) | Accepted | Not accepted | Accepted |
| EMC | Accepted | Accepted | Not accepted | Accepted |
| YML | Accepted (advance booking) | Accepted | Not accepted | Accepted |
| CMA CGM | Accepted (advance booking) | Accepted | Case-by-case | Accepted |
Note: "Accepted" = routinely handled. "Advance booking" = requires booking 5-7 working days before vessel cut-off. "Restricted" = only on specific routes/vessels. "Not accepted" = carrier does not carry this sub-division. Always confirm current policy with your freight forwarder before booking — carrier policies change.
China Export Process for Class 2 Gases
Exporting Class 2 gases from China follows the standard DG export workflow with additional cylinder-specific requirements:
- MSDS Preparation: Obtain a GHS-compliant Material Safety Data Sheet from the manufacturer. The MSDS must identify the correct UN number, hazard class, and emergency response procedures.
- DG Packaging Certificate (危包证): The cylinder must have a valid Chinese DG Packaging Performance Certificate issued by an authorized inspection body (typically CIQ/CCIC). This certificate confirms the pressure receptacle meets UN standards. Validity periods vary.
- Cylinder Periodic Inspection Report: For refillable cylinders, the latest hydrostatic test certificate (钢瓶检验报告) must be current. Expired cylinders cannot be shipped.
- Maritime DG Declaration: File the Maritime Dangerous Goods Declaration with the local MSA (Maritime Safety Administration) 24-48 hours before vessel loading. The declaration must cite the correct UN number, class, packing group (if applicable), and vessel/voyage details.
- Port Filing: Register the DG shipment with the port authority. Qingdao Port has a dedicated DG acceptance process that takes 1-2 working days.
- Carrier DG Booking: Submit DG cargo details (UN number, number of cylinders, total weight, stowage category) to the carrier at least 5-7 working days before the intended sailing.
- Container Stuffing: Cylinders must be loaded upright (valves up), properly secured to prevent movement, and segregated according to IMDG stowage and segregation requirements.
Port Recommendations
For Class 2 gas exports from China, Qingdao Port is the preferred loading port. Qingdao has dedicated DG storage yards with proper ventilation and fire separation, well-established cylinder inspection facilities near the port, and the highest sailing frequency for Asia, South America, and Africa routes. Shanghai is the best alternative for Europe and North America destinations with the widest carrier choice. Tianjin serves northern China origins.
For Class 2.3 (toxic gases), Qingdao is strongly recommended — it has the most experienced handling personnel and the most DG-friendly port authority acceptance process for toxic gas shipments.
Documentation Checklist
- MSDS (Material Safety Data Sheet) — GHS format, current version
- DG Packaging Certificate (危包证) — issued by authorized inspection body
- Cylinder Periodic Inspection Report (钢瓶检验报告) — valid test certificate
- Maritime DG Declaration — filed with MSA
- Port DG Filing Approval
- Commercial Invoice and Packing List (with DG notation)
- Bill of Lading (B/L) — with DG endorsement
- Carrier DG Booking Confirmation
- Leak Test Record (per cylinder or per batch)
Frequently Asked Questions
Can I ship half-empty or used gas cylinders from China?
Yes, but with conditions. Partially filled cylinders are still classified as Class 2 DG and require the same documentation. Empty, uncleaned cylinders that previously contained hazardous gas are also classified as Class 2 and must be shipped with valves closed and caps in place. Only thoroughly cleaned and purged cylinders with a cleaning certificate may ship as non-DG.
What is the difference between compressed, liquefied, and refrigerated liquefied gas for shipping purposes?
These are physical states that affect cylinder specifications: Compressed gas (e.g., oxygen, nitrogen) remains gaseous in the cylinder at normal temperature under pressure. Liquefied gas (e.g., propane, chlorine) is liquid in the cylinder under pressure at normal temperature. Refrigerated liquefied gas (e.g., liquid nitrogen, LNG) is kept liquid at low temperature in cryogenic containers with venting. Each type has different UN pressure receptacle standards, fill limits, and venting requirements.
Can Class 2 gases ship by air freight from China?
Limited — most Class 2 gases are prohibited or severely restricted on passenger aircraft. On cargo-only aircraft, some 2.2 non-flammable gases may be accepted under IATA DGR with strict quantity limits. Flammable (2.1) and toxic (2.3) gases are almost never accepted for air freight. Sea freight is the primary and most practical mode for Class 2 exports from China.
Do you handle refrigerant gas (HFC/HFO) exports from China?
Yes. Refrigerant gases are typically Class 2.2 under UN1078 (non-flammable) or UN3159 (non-flammable, with specific provisions). China is the world's largest producer of refrigerants (R-134a, R-410A, R-32, etc.). We handle regular refrigerant gas exports in ISO tank containers, cylinder packs, and individual cylinders. Carrier acceptance is generally good for 2.2 refrigerant gases. Note that some newer refrigerants (e.g., R-290 propane, R-32) may be classified as 2.1 (flammable) and require different handling.