What does H420 mean?

Categories and label elements

CLP abbreviation	Pictogram	Signal word
Ozone 1	GHS07Exclamation mark	Warning

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.

When does a mixture need H420?

H420 reaches the label and the safety data sheet of a mixture only when the classes and percentages of its components pass certain limits. The relevant limits in the Chemoris rule file are:

• Threshold method: a Ozone 1 component at ≥ 0.1 % gives the mixture the same class.
• If a component has a harmonised specific concentration limit (SCL) and meets it, the mixture takes the corresponding class directly.

For a step-by-step worked example see classifying a mixture under CLP.

Where is H420 written in the SDS?

In the SDS, H420 ("Harms public health and the environment by destroying ozone in the upper atmosphere") first enters Section 2.1 as a classification, written as "Ozone 1" together with the code. Section 2.2 then gives its full text as a label element. Components that have this class are listed row by row in the Section 3 table; in addition, it is justified in Section 12 (ecological information) under the relevant effect heading.

How does H420 appear on the label?

On the label H420 appears with the pictogram GHS07 (exclamation mark), and it is written with the signal word "Warning". 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, 1 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 H420 are given together.
• Section 2.2: label elements; H420 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 H420

The values below come from the Chemoris rule file (CLP Annex I). They show the condition under which H420 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.

H420 compared with H413 and H412

The table below puts H420 next to its closest neighbouring statements; the values are read from the rule data.

The signal word differs: Warning for H420, — for H413. The pictogram differs: GHS07 for H420, none for H413. The signal word differs: Warning for H420, — for H412. The pictogram differs: GHS07 for H420, none for H412.

H413 H412

In which SDS sections does H420 appear?

H420 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 H420

H420 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 1 candidates for this class:

The GHS07 pictogram and “Warning” 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 H420 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 H420 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 H420

• Printing too many pictograms: If the skull and crossbones (GHS06) applies, the exclamation mark (GHS07) is not used at all (CLP Article 26(1)(b)).
• Mixing up signal words: if any class requires “Danger”, only “Danger” is printed and “Warning” drops out (CLP Article 20(3)).
• 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 H420 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.

Frequently asked questions