Class 4 · Flammable Solids

Class 4 Flammable Solid Ocean Freight

IMDG-certified shipping for flammable solids, spontaneously combustible materials, and water-reactive substances — including matches, sulfur, activated carbon, and calcium carbide.

Three Sub-Divisions of Class 4

Class 4 covers solids that ignite easily, self-heat, or react dangerously with water. The shipping rules differ significantly between the three sub-divisions, and carriers often treat them as separate cargo types.

4.1 Flammable Solids

Solids that readily ignite and sustain combustion: safety matches (UN1944), sulfur (UN1350), nitrocellulose, dry cellulose products.

4.2 Spontaneously Combustible

Materials that self-heat on contact with air: white phosphorus, activated carbon (UN1362), wet cotton or linen waste, oily rags.

4.3 Dangerous When Wet

Release flammable gas on contact with water: calcium carbide (UN1402), sodium, potassium, magnesium pellets, lithium metal.

Class 4 Cargoes We Ship

Activated Carbon & Adsorbents

Granular activated carbon for water treatment and air filtration. Classed as 4.2 when shipped in bulk or in certain packaging. Requires ventilation to prevent self-heating.

Sulfur & Sulfur Compounds

Elemental sulfur (UN1350) in pellets or powder. Common in chemical and fertilizer supply chains.

Calcium Carbide & Metals

Calcium carbide (UN1402) for acetylene production, magnesium granules, alkali metals. Must be hermetically sealed — any water ingress is dangerous.

Powdered Chemicals & Desiccants

Various powdered industrial chemicals that fall under 4.1 or 4.3 based on their SDS classification. We review each product individually.

Non-Negotiable Shipping Rules

Moisture protection is critical for 4.3. Water-reactive cargo must be hermetically sealed. Container must be dry, clean, and free of residues.
4.2 needs ventilation. Self-heating materials require ventilated containers or temperature monitoring to prevent thermal runaway.
Segregation from oxidizers. Class 4 cannot share a container with Class 5.1 oxidizers or Class 8 strong acids.
MSDS must state fire and water reactivity. If these are missing from your SDS, we cannot book the cargo.

Shipping Flammable Solids or Water-Reactive Chemicals?

Send us your MSDS. We confirm classification, packaging, and stowage options within 4 business hours.

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Class 4 Flammable Solids FAQ

Is activated carbon always a dangerous good?

Activated carbon is Class 4.2 (spontaneously combustible) when shipped in bulk or in certain packagings, because it can self-heat when impregnated with oils or exposed to moisture. We confirm based on the SDS and packaging.

Can calcium carbide ship in LCL consolidation?

We generally book 4.3 water-reactive cargoes in FCL only, because any moisture or residue in a shared container is a safety risk. LCL is considered case by case.

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