Class 4 labels: flammable solids (striped, half red or blue)
The package contains a flammable solid (4.1: matches, firelighters, some powders), something that can catch fire by itself in air (4.2: oily cloths, some metal powders, charcoal) or something that gives off flammable gas in contact with water (4.3: sodium, calcium carbide).
Who puts it on the box
The sender (consignor).
How to read it
Tell the three apart by the background: stripes, half white half red, or blue. A blue 4.3 package must be kept dry and never put out with water.
What it does not promise
It does not promise the contents are stable if the packaging is damaged, and it does not name the substance: the UN number and name on the box and documents do.
A mark on a parcel is the sender’s statement about what is inside and how it should be handled. It is not a certificate that the parcel is packed safely, that anyone handled it as marked, or that your carrier accepts it: for what you may send, read the carrier’s own terms.
- What it looks like
- Three labels with a flame and the figure 4: 4.1 flammable solid, red and white vertical stripes; 4.2 spontaneously combustible, white top half and red bottom half; 4.3 dangerous when wet, blue.
- Regulation
- ADR 2025, 5.2.2.2.2, label models No. 4.1, 4.2 and 4.3; UN Model Regulations 5.2.2.2.2
- Kind of mark
- A dangerous-goods mark or label from the UN Model Regulations, applied in Europe by ADR (road) and its sister agreements for rail and waterways, and on the same pattern by the US 49 CFR. It says the package holds dangerous goods.
- Also called
- Flammable solid label; Spontaneously combustible label; Dangerous when wet label
Related
Other marks with the same shape
Sources
Each document was fetched and read on the date shown. Written in our own words; quotations are the documents’ wording.
- Regulator guidance — Health and Safety Executive (UK regulator for the carriage of dangerous goods): Carriage of dangerous goods manual — Consignment procedures: marking and labelling of packages (ADR 5.2) — Package labels are the “hazard diamonds” of ADR 5.2.2 with the class number; specimen labels are in ADR 5.2.2.2.2 and sizes in 5.2.2.2.1.1; the consignor is responsible for marking and labelling. Checked 2026-09-27.
- Law adopting the same mark — US Government Publishing Office (govinfo), 49 CFR, edition of 1 October 2024: 49 CFR Part 172 Subpart E — Labeling (§§ 172.400–172.450, the hazard class labels) — §§ 172.420–172.423: FLAMMABLE SOLID (white with vertical red stripes), SPONTANEOUSLY COMBUSTIBLE (upper half white, lower half red) and DANGEROUS WHEN WET (blue). Labels are at least 100 mm on each side with an inner border about 5 mm inside the edge (§ 172.407). Checked 2026-09-27.