Physical hazard · Flammable gases
H231 — May react explosively even in the absence of air at elevated pressure and/or temperature
Physical hazard statements describe what the substance itself can do — explode, ignite, react, corrode metal. No substance with a harmonised EU classification carries this code.
01 · Wording
What H231 says
May react explosively even in the absence of air at elevated pressure and/or temperature.
CLP Annex III · Physical hazards
Flammable gases GHS chapter 2.2
Category Chemically unstable B · pictogram GHS02 (flame) · signal word Danger
Introduced in Rev.4 (2011).
Added by UN GHS Rev.4 and unchanged through Rev.11 (2025). Jurisdictions that sit on an earlier revision do not have this code at all.
Nine editions of the UN model text, 86 hazard statements, 19 of which ever moved. Read the full story in what changed in UN GHS Rev.11.
02 · Legal status
Where H231 is current
GHS is a United Nations model text, revised every two years, and each jurisdiction adopts a revision on its own timetable. A code can be legally current in one system and deleted in another — that is normal, not an error.
| Jurisdiction | Basis | Status of H231 |
|---|---|---|
| EU CLP | Regulation (EC) 1272/2008 CLP Annex IV, Part 2 (consolidated) | Current |
| US OSHA HazCom | 29 CFR 1910.1200 Appendix C UN GHS Rev.7 (final rule of 20 May 2024) | Current |
| US HazCom 2012 | legacy · GHS Rev.3 UN GHS Rev.3, Annex 3 | not in this system |
| UN GHS | Rev.11 (2025) UN GHS Rev.11, Annex 3 | Current |
Currently in force under: EU CLP, US OSHA HazCom, UN GHS. Sources: EU CLP · US OSHA HazCom · US HazCom 2012 · UN GHS
03 · Substances
Substances carrying H231
No substance with a harmonised classification in CLP Annex VI carries this code. That does not mean it is unused — suppliers apply it to their own mixtures.
All hazard statements
The full list of H-codes with the jurisdiction switch lives on the hazard statements hub. For what to do about the hazard, see precautionary statements (P-codes).
Wording quoted from the regulation named above. Substance counts come from harmonised classifications in CLP Annex VI — the statements on a real product also depend on the supplier's own classification. Always check the supplier safety data sheet.