What does H251 mean?

Categories and label elements

CLP abbreviation	Pictogram	Signal word
Self-heat. 1	GHS02Flame	Danger

Related precautionary statements (P codes)

The precautionary statements that CLP Annex IV assigns to this class. Not all of them go on the label: under CLP Article 28(3), no more than six precautionary statements appear on the label unless the nature and severity of the hazard require more; the selection depends on the product and its users.

Where is H251 written in the SDS?

In the prepared SDS the class "Self-heat. 1" is matched with the code in Section 2.1, the text of H251 is written in Section 2.2 next to the pictogram and signal word, and the class of the component shows up in Section 3. Section 16 collects the full text of the H statements cited by code. For H251, it must agree with the physical and chemical properties in Section 9 and, if the product is subject to transport rules, it is read together with the ADR information in Section 14.

How does H251 appear on the label?

When you see H251 on a label it is accompanied by GHS02 (flame), and it is written with the signal word "Danger". In the Chemoris template Section 2.2 carries at most 8 H statements; if the limit is exceeded the least severe ones are dropped and a warning is shown. For the bottom of the label, 5 P statements are candidates for this class in CLP Annex IV; under CLP Article 28 at most 6 of them are selected.

Where does it appear in the safety data sheet?

• Section 2.1: classification; the class abbreviation and H251 are given together.
• Section 2.2: label elements; H251 with its full text, pictogram and signal word.
• Section 3: composition table; in the row of every component that has this class.
• Section 16: the full text of the H statements cited as codes in earlier sections.

Class criteria and thresholds for H251

The values below come from the Chemoris rule file (CLP Annex I). They show the condition under which H251 arises in a mixture. For physical hazards and other classes that depend on test data, the result comes from the mixture's own measurement, not from component percentages.

The class behind H251 depends on the mixture's own test data; the Chemoris rule file does not derive it from component percentages and warns the chemist when a component carries it (≥ 1 %) (CLP Annex I 2.x (for physical hazards 1.1.1.3 / Article 6(5) data requirement); 2.16.3 (metal-corrosive mixture)).

H251 compared with H252 and H250

The table below puts H251 next to its closest neighbouring statements; the values are read from the rule data.

The signal word differs: Danger for H251, Warning for H252. Both are shown with the same pictogram (GHS02). H251 and H250 carry the same signal word (Danger). Both are shown with the same pictogram (GHS02).

H252 H250

In which SDS sections does H251 appear?

H251 does not stay only in the label section of an SDS; the class itself and the precautionary statements assigned to it shape the content of other sections too. The counts are calculated from the P statements that Annex IV assigns to this class.

Statements that appear on the label together with H251

H251 is never printed alone on a label; it sits next to the pictogram and the signal word. The Chemoris selection method (response, prevention, storage, disposal in that order; core statements first) gives these first 5 candidates for this class:

The GHS02 pictogram and “Danger” are printed together. This ranking applies because a label usually carries at most 6 statements; when a combined statement is selected, its parts are not printed again.

Official EU wording of H251 in other languages

When a product is exported to the EU, the SDS and label are expected in the official language of the Member State where it is placed on the market (REACH Article 31(5)). The table gives the official wording of H251 from the CLP Annex III/IV language versions published in the Official Journal of the European Union. Source: EUR-Lex CELEX 02008R1272-20260701.

Common mistakes with H251

• Deriving the class from percentages: H251 cannot be calculated from component percentages; the mixture's own test data is required (CLP Annex I 2.x (for physical hazards 1.1.1.3 / Article 6(5) data requirement); 2.16.3 (metal-corrosive mixture)).
• Writing unlimited H statements for a multi-class product: in the Chemoris template, Section 2.2 holds at most 8 H statements.

Next steps

To read a statement like H251 correctly on a label and in an SDS, see the guide How to read H and P codes; to pick the class and prepare the label automatically, use the free label tool.

Related hazard statements

Other H statements in the same hazard family as H251 (Self-heat.). The difference between categories mostly comes from the degree of severity.

• H252Self-heating in large quantities; may catch fire.

Frequently asked questions