H231 · Hazard statementMay react explosively even in the absence of air at elevated pressure and/or temperature

Hazard statementPhysical

H231 is the GHS hazard statement “May react explosively even in the absence of air at elevated pressure and/or temperature”. It is used for Flammable gases (chapter 2.2), Category 1A, chemically unstable gas B. The English wording is the same as UN GHS Rev.11 in US OSHA, EU CLP and Canada. Canada’s official French text is “Peut exploser même en l’absence d’air à une pression et/ou température élevée(s)” and Mexico’s Spanish text is “Puede explotar incluso en ausencia de aire, a presión y/o temperaturas elevadas”. The UN GHS Rev.11 label matrix lists 5 precautionary statements for it (UN only).

Maintained by Valenc. Data checked 2026-10-20.

Heading text: UN GHS Rev.11 Annex 3. Wording can differ by jurisdiction; see the table below.

Wording by jurisdiction

UN GHS Rev.11

Same as UN

GHS Rev.11 (2025), Annex 3

May react explosively even in the absence of air at elevated pressure and/or temperature

UN GHS Rev.11, Annex 3, Table A3.1.1, PDF p. 303

US OSHA HCS

Same as UN

HCS 2024 · primarily GHS Rev.7, some Rev.8

May react explosively even in the absence of air at elevated pressure and/or temperature.

29 CFR 1910.1200 App. C, matched by wording

EU CLP

Same as UN

EU_CLP_2025 · consolidated 1 Jul 2026

May react explosively even in the absence of air at elevated pressure and/or temperature.

EU CLP (Reg. (EC) No 1272/2008), Annex III, Part 1

Canada (EN)

Same as UN

WHMIS_2022 · GHS Rev.7 (Rev.8 for chemicals under pressure)

May react explosively even in the absence of air at elevated pressure and/or temperature

GHS Rev.7 Annex 3 Table A3.1

Canada (FR)

Adopted

WHMIS_2022 · SGH Rév.7, texte officiel

Peut exploser même en l’absence d’air à une pression et/ou température élevée(s)

GHS Rev.7 Annex 3 Table A3.1

Mexico (ES)

Adopted

NOM-018-STPS-2015 · GHS 5th revised edition

Puede explotar incluso en ausencia de aire, a presión y/o temperaturas elevadas

Gases inflamables (incluidos los gases químicamente inestables) · B (gas químicamente inestable)

NOM-018-STPS-2015, DOF 9 October 2015, Apéndice C, Tabla C.1, PDF p. 30

Hazard classes and categories

Flammable gases (chapter 2.2) · Category 1A, chemically unstable gas B

UN GHS Rev.11 Annex 3, sections 1 and 2

FRGaz inflammables (chapitre 2.2) · catégorie 1A, chemically unstable gas B

ESGases inflamables (incluidos los gases químicamente inestables) · B (gas químicamente inestable) (NOM-018-STPS-2015)

Pictogram: Flame (GHS02)

UN GHS Rev.11 Annex 3, section 3. Pictogram rules can differ by jurisdiction; see the GHS pictogram guide.

P statements in the UN GHS Rev.11 label matrix only

UN GHS Rev.11 only. EU CLP, US OSHA, Canada (GHS Rev.7) and Mexico assign different P statements; check the regulation for your market.

Flammable gases (chapter 2.2) (chemically unstable gases), categories 1A, chemically unstable gas A, 1A, chemically unstable gas B (PDF p. 347)
P203 P210 P377 P381 P403

UN GHS Rev.11 Annex 3, section 3. Each table covers the categories named; a P statement may apply to only some of them. Many apply only under conditions; check the conditions for use before putting them on a label.

Related codes

H220 H230

Change in UN GHS Rev.11

No change to the wording or the hazard classes in Annex 3 compared with Rev.10.

Sources

Each cell in the table names the official table and page for H231. Full citations, links and revision notes for UN GHS Rev.11, US OSHA, EU CLP, Canada and Mexico: Sources and revision notes.

These are regulatory phrases for labels and safety data sheets. Check them against the official source for your jurisdiction before use.