Dichloromethane (DCM, CAS 75-09-2): Specification Grades, UN Packing Requirements, and Export Documentation

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

The short version: Dichloromethane is a single substance with three commercially distinct specification grades, a Class 6.1 toxic classification, and a low boiling point (39.6 °C) that makes packaging selection a pressure problem rather than a container-volume problem. This note sets out the parameter set that defines each grade, the analytical method behind each parameter, the UN packing rules, and the document set that must be arithmetically consistent at export.

1. Identity and Physical Constants

Two technical points often missed: DCM’s vapour is ~2.9× heavier than air and will accumulate in pits and low areas; and although it has no flash point under standard test conditions, it can be made to burn at high oxygen concentration or elevated temperature — the correct statement is “no flash point by standard method”, not “non-flammable”.

2. Specification Grades and the Parameters That Define Them

Note on stabilisers: DCM hydrolyses slowly in the presence of water and light, producing HCl. Commercial grades add a small amount of stabiliser (commonly a low-boiling amine or amylene class compound). A COA that reports assay without stating the stabiliser content is incomplete — the stabiliser is part of the specification and affects the effective purity.

3. Analytical Methods Behind Each Parameter

The COA literacy point (developed in Reading a Chinese Chemical COA): a spec line reading “conforms” without a measured value, method, and limit of quantification is a claim. The value of the COA lies in the raw numbers and the method attached to each.

4. UN Packing Requirements — Why DCM’s Boiling Point Drives the Choice

DCM boils at 39.6 °C. A container in tropical service routinely exceeds 50 °C internal temperature. The vapour pressure at 55 °C is far above atmospheric, so the packaging must be pressure-rated, not merely liquid-tight.

Filling ratio rule (IMDG 4.1.1.11 for IBCs): leave ≥ 2 % ullage at 55 °C, and calculate the fill for the maximum expected transport temperature, not the loading temperature. Loading cold in winter and shipping through the tropics is the classic overfill scenario. The stowage side of the same rule — segregation by class, cylinder grouping and temperature compensation inside one container — is set out in Dangerous Goods Mixed Loading.

Also required: the packaging must carry a UN mark with the correct packaging code, test pressure (for pressure-rated designs), year of manufacture, and country authorising the mark. See Dangerous Goods Mixed Loading for how to decode the mark element by element.

5. Export Documentation — the Consistency Requirement

Export of DCM involves four documents whose data must agree arithmetically:

Cross-check failures that stop a shipment:

• Proper shipping name mismatch — the transport name must match the IMDG entry for UN 1593, not the trade name.
• Class disagreement between SDS and DG declaration — both must state 6.1.
• REACH registration absent for the EU importer — the obligation sits with the importer (or their Only Representative), not the Chinese exporter; a shipment without it is not admissible for the EU.
• Tonnage band inconsistency — the registration tonnage must cover the annual volume being shipped.

6. Occupational and Environmental Limits (destination-dependent)

• DCM is IARC Group 2A. Occupational exposure limits vary materially by jurisdiction (e.g. EU indicative OEL 100 ppm 8-h TWA with skin notation; several jurisdictions apply stricter values or specific prohibitions in consumer products).
• EU restrictions on DCM in paint strippers apply to consumer and, with conditions, professional use — a product-application restriction distinct from transport regulation.
• Ventilation during unstuffing is required; the vapour is heavier than air and accumulates at floor level.

6b. Which grade to specify — and what the wrong choice costs

The three grades differ in ways that change how the product has to be handled, not only its price. Two of the parameters decide most of it: water and acidity.

Three practical rules follow:

• Specify water at a sampling point. Karl-Fischer results move with handling and sampling; a limit without a sampling point is not comparable between suppliers.
• State whether the product is stabilised, and at what level. A stabilised and an unstabilised DCM are not the same article, and the stabiliser content is part of the specification.
• Write the assay basis. Area-% and mass-% are not interchangeable, and a grade name alone does not state which was used.

7. Preparing a DCM export shipment — step by step

1. Fix the specification by grade. State the parameter limits with their methods — assay basis (area-% or mass-%), Karl-Fischer water, acidity as HCl, residue on evaporation and the stabiliser content. A grade name on its own is not a specification.
2. Set the identity triple. Name, CAS 75-09-2 and UN 1593 written identically on every document; the transport name must be the IMDG entry for UN 1593, not the trade name.
3. Choose pressure-rated packaging for the maximum expected transport temperature. Closed-head steel drums (1A1), UN-marked steel or composite IBCs (31A / 31H1 / 31H2), or an approved ISO tank. Open-head drums and glass are not acceptable for transport quantities.
4. Compute the fill at the maximum transport temperature, not the loading temperature. Leave ≥ 2 % ullage at 55 °C for IBCs and never fill to liquid-full — loading cold in winter and shipping through the tropics is the classic overfill case.
5. Verify the packaging mark and the cylinder date. Packaging code, test pressure, year of manufacture and authorising country; for cylinders, a current hydrostatic test date.
6. Reconcile the document set arithmetically. Invoice, packing list, COA, SDS and DG declaration must agree on name, CAS, UN number, class 6.1, packing group III and net weight per package; for the EU, confirm a REACH registration (or Only Representative) covering the tonnage band.
7. Release only when every figure above reconciles. A single mismatch — a class disagreement between the SDS and the DG declaration, or a missing EU registration — stops the shipment.

Technical reference on dichloromethane specification, packing and export documentation. Limits shown are commonly published specification ranges and vary by producer and destination; the governing standard for a given shipment, and the applicable IMDG edition, control in case of conflict. Occupational and product restrictions differ by jurisdiction — verify for the destination market.

FAQ

What is DCM’s boiling point and why does it matter for shipping? 39.6 °C. Container internal temperatures routinely exceed 50 °C in tropical service, so the packaging must be pressure-rated (closed-head steel drums or UN-marked IBCs), not merely liquid-tight.

What are the UN details for dichloromethane? UN 1593, Class 6.1 (toxic), Packing Group III. The transport proper shipping name must match the IMDG entry, not the trade name.

What water content defines the solvent grade? Solvent/industrial grade generally specifies ≤ 0.02 % (200 ppm) by Karl-Fischer; pharmaceutical grade ≤ 0.01 %. The sampling point must be stated for the figure to be comparable.

What we can provide

Dichloromethane is supplied against one of three specification grades, and a grade is defined by its parameter set — so we quote the parameters, not the grade name alone:

On the same basis we can state:

• Assay and residue — the assay figure with its basis (area-% or mass-%) and the GC conditions, plus residue on evaporation for the grade supplied.
• Stabiliser content — reported as part of the specification; a stabilised product and an unstabilised one are not the same article.
• Batch documentation — the certificate of analysis for the batch actually shipped, with the batch number matched to the drum or IBC label.
• Grade alignment — where your specification is written to different water or acidity limits, which supplying grade the limit maps to and where the figure sits against it.

Contact us with: the grade, the parameter limits your specification sets, and the destination market.

Sources

• PubChem — Dichloromethane, Compound CID 6344 (US National Library of Medicine): identity, CAS 75-09-2 and physical constants — https://pubchem.ncbi.nlm.nih.gov/compound/6344
• IARC Monographs on the Identification of Carcinogenic Hazards to Humans — List of Classifications (WHO / IARC): dichloromethane, Group 2A — https://monographs.iarc.who.int/list-of-classifications
• IMDG Code (International Maritime Organization): packing instructions P001 / IBC02, the UN packaging mark and the IBC filling-ratio rules — https://www.imo.org/
• CAS Registry Number — format and check-digit algorithm (CAS, a division of the American Chemical Society) — https://www.cas.org/

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