GHS hazard statement
H231: May react explosively even in the absence of air at elevated pressure and/or temperature
- H231
- Physical hazards
- Danger
H231 means “May react explosively even in the absence of air at elevated pressure and/or temperature”. It is a GHS hazard statement for Flammable gases (1A, Chemically unstable gas B), shown with GHS02 under the signal word “Danger”.
Hazard class and category
| Hazard class | Category | Pictogram | Signal word | UN transport class |
|---|---|---|---|---|
| Flammable gases | 1A, Chemically unstable gas B |  | Danger | Div 2.1 |
What H231 means
Flammable gases are gases that form a flammable mixture with air at 20 °C and a standard pressure of 101.3 kPa.
A leak can create an explosive atmosphere, and the gas can ignite from a spark, hot surface or flame some distance from the source. Many flammable gases are also stored under pressure.
What to do
Keep away from all ignition sources, ventilate the area, use only explosion-protected equipment where required, and do not extinguish a gas fire unless the leak can be stopped safely, because the unburnt gas can re-ignite or explode.
This is general guidance for the hazard class. The safety data sheet for your product always takes precedence.
Precautionary statements for H231
The GHS lists these precautionary statements for this hazard. Which ones appear on a label depends on the supplier's classification.
Chemicals carrying H231
No chemicals in our database are classified with H231 yet.
H231 frequently asked questions
What does H231 mean?
H231 means "May react explosively even in the absence of air at elevated pressure and/or temperature". It is a GHS hazard statement in the physical hazards group, covering Flammable gases (1A, Chemically unstable gas B).
Which pictogram goes with H231?
H231 is shown with GHS02 (Flame).
What signal word goes with H231?
The signal word for H231 is "Danger".
Which precautionary statements go with H231?
The GHS data lists 5 precautionary statements for H231, including P203, P210, P337, P381, P403. They cover prevention, response, storage and disposal. The full list is on this page.
Hazard statements describe the hazard of a classified substance or mixture. The classification of a specific product can differ, so use the supplier's SDS.
https://pubchem.ncbi.nlm.nih.gov/ghs/ghscode_10.txt (UN GHS Revision 10, retrieved 2026-10-12)