Dangerous Goods Mixed Loading for Refrigerants and Solvents: IMDG Segregation, UN Marks, and Cylinder Stacking

Mon, 07 Sep 2026 · HARMONY TECHNOLOGY (ZHEJIANG) CO., LTD.

Dangerous Goods Mixed Loading for Refrigerants and Solvents: IMDG Segregation, UN Marks, and Cylinder Stacking

The short version: Loading Class 2.2 refrigerants together with Class 6.1 chlorinated solvents in one container is routine export practice, but it is governed by several independent technical constraints that are often conflated: IMDG segregation rules, UN packaging-mark decode, cylinder pressure–temperature limits, and IBC filling ratios. Each has a different controlling document, and getting one wrong invalidates the others.

1. Which Classes Are Actually Involved

First technical point: each refrigerant has its own UN entry — they are not interchangeable on a manifest. Single-substance refrigerants carry a dedicated UN number (R134a = UN 3159, R32 = UN 3252, R22 = UN 1018); blends are classified differently: R410A ships as UN 3163 LIQUEFIED GAS, N.O.S., while R407C has its own dedicated entry UN 3340 REFRIGERANT GAS R 407C. A manifest that treats “refrigerant” as one line item, or that reuses a single UN number across products, will be rejected — the UN number and class together drive the packing instruction and the segregation table.

2. IMDG Segregation — What Actually Applies Within One Container

IMDG segregation is expressed in four degrees: away from (1), separated from (2), separated by a complete compartment or hold from (3), separated longitudinally by an intervening complete compartment (4).

Within a single container/CTU, degrees 3 and 4 are generally unachievable — there is no intervening compartment. In practice, degrees 1 and 2 are the operable ones and must be satisfied by stowage geometry (distance, physical separation, or an intervening non-DG stow).

The controlling document is the carrier’s DG acceptance policy, which may be stricter than IMDG’s minimum. Written pre-approval from the line is what makes the stow legally executable — not the IMDG table alone.

3. UN Packaging Marks — Decoding Them

A UN mark on a cylinder or drum is not decorative; each element is a technical statement:

UN 4BA 250 / 23 / CN / M4621 / TPED
│  │   │    │    │      │
│  │   │    │    │      └─ Approval (or national scheme, e.g. TPED/ADR)
│  │   │    │    └──────── Manufacturer's serial / approval ref
│  │   │    └───────────── Country authorising the mark
│  │   └────────────────── Year of manufacture (23 = 2023)
│  └────────────────────── Test pressure, in bar
└───────────────────────── Packaging type code (4BA = steel cylinder, welded)

What to check before loading:

• Year of manufacture + the periodic inspection interval — gas cylinders typically require hydrostatic re-test every 5 or 10 years depending on the scheme; an expired test renders the cylinder unshippable regardless of contents.
• Test pressure ≥ the design minimum for the fill — for refrigerants, this is well above the saturation pressure at 55 °C reference temperature.
• Country authorising the mark — affects whether the destination accepts the certification scheme.

4. Cylinder Stacking and Pressure Limits

The overfill mechanism, stated precisely: a liquefied-gas cylinder filled without vapour space reaches liquid-full condition at some temperature below the design reference. Beyond that point, pressure rises hydrostatically — hundreds of bar for a few degrees — far faster than the relief device can respond. This is why filling ratio, not pressure rating alone, is the controlling number.

5. IBC Filling Ratios and Temperature Compensation

For DCM and other Class 6.1 liquids in IBCs or drums:

Practical consequence of DCM’s low boiling point (39.6 °C): in a container on deck in tropical sun, internal temperatures can exceed 50 °C. A non-pressure-rated drum or IBC is not acceptable for DCM regardless of fill level. Which packaging satisfies that requirement, and the grade parameters that travel with the shipment, are set out in Dichloromethane: specification grades, packing and export documentation.

6. Ventilation, Temperature and Stow Position

• Class 2.2 cylinders in a closed container: no forced ventilation is required for non-flammable, non-toxic gases, and a CTU that has held 2.2 cylinders is not oxygen-deficient. Oxygen displacement is a separate case, not a property of Class 2.2: it applies where a Class 2.1 cylinder has leaked inside the unit, or where a large 2.2 charge is released into an enclosed space during stripping — in those situations, treat the atmosphere as an oxygen-deficiency hazard and test it before entry.
• Class 6.1 solvents: adequate ventilation during unstuffing is required; DCM’s occupational exposure limits are low (see the product’s MSDS under the destination’s national OEL).
• Stow position: cylinders upright with valves protected; solvents in IBCs on pallets, secured against longitudinal movement per the CTU Code.

Technical reference on dangerous-goods stowage for refrigerant and chlorinated-solvent cargoes. Requirements differ by mode (IMDG for sea, ADR/RID for road/rail, IATA for air) and by carrier. This note describes IMDG sea-transport constraints; the applicable edition for a given shipment and the carrier’s own DG policy govern in case of conflict.

What we can provide

For a mixed cargo we can supply the loading and segregation plan for the actual combination, built from the classes and UN numbers above:

• Segregation by combination — which pairs move as “away from” or “separated from” inside one CTU, and the stow geometry used to satisfy each degree (cylinder group separation, an intervening non-DG stow, opposite-end stowing).
• Packaging and mark check — packaging code, test pressure, UN mark and cylinder hydrostatic test date verified per product before loading.
• Filling-ratio calculation — cylinder filling ratios per P200 for each gas, and IBC or drum ullage calculated for the maximum expected transport temperature rather than the loading temperature.
• Transport data set — UN number, class, packing group, proper shipping name and packing instruction for every line in the container, so carrier pre-approval can be sought against stated data rather than assumed.

Contact us with: the product list with quantities, the packaging types, and the loading and discharge ports.

Prepared by HARMONY TECHNOLOGY (ZHEJIANG) CO., LTD. — trading company; the group’s operating entity for this product line.