Flammable

The Broadest Physical-Hazard Pictogram in GHS

No other pictogram spans as many hazard classes as the GHS02 flame. It is assigned to flammable gases of Category 1 (split into 1A and 1B in newer GHS revisions), aerosols of Categories 1 and 2, flammable liquids of Categories 1 to 3, and flammable solids of Categories 1 and 2. It also covers pyrophoric liquids and solids, self-heating substances, substances that emit flammable gases on contact with water, self-reactive substances and organic peroxides of Types B through F, and desensitized explosives.

The unifying idea is ignition under normal or foreseeable conditions, but the mechanisms differ sharply. A Category 2 flammable liquid such as acetone ignites from an external spark; a pyrophoric reagent such as tert-butyllithium ignites spontaneously in air within minutes; a water-reactive material such as calcium carbide generates flammable acetylene when wetted. The flame alone does not tell you which mechanism applies, so the hazard statement on the label and Section 2 of the safety data sheet must always be read with it.

Categories, Signal Words, and Example H-Statements

Flammable liquids illustrate how the category drives the signal word. Categories 1 and 2 (flash point below 23 °C) take Danger with H224 (extremely flammable liquid and vapour) or H225 (highly flammable liquid and vapour); Category 3 (flash point between 23 °C and 60 °C) takes Warning with H226 (flammable liquid and vapour). Category 4 liquids, recognized under GHS and OSHA HazCom but not under EU CLP, carry H227 with no pictogram at all.

Other classes bring their own statements: H220 for extremely flammable gases, H222 for extremely flammable aerosols, H228 for flammable solids, H250 for pyrophoric materials, H251 and H252 for self-heating substances, and H260 or H261 for water-reactive materials that emit flammable gases. Because these codes map to very different storage rules — inerting for pyrophorics, moisture exclusion for water-reactives, temperature control for self-reactives — the H-statement is the operative instruction, and the flame pictogram is the attention-getter.

Regulatory Context: OSHA HazCom 2012 and EU CLP

Under 29 CFR 1910.1200, every shipped container of a flammable-classified chemical must display the GHS02 pictogram in a red diamond frame, and the classification feeds directly into other OSHA rules: flammable liquid categories determine storage limits under 29 CFR 1910.106, and the flammability data drive area classification for electrical equipment. OSHA's 2024 HazCom update, which aligned the standard mainly with GHS Revision 7, refined flammable gas subcategories and added aerosol Category 3, which carries H229 without the pictogram.

The EU CLP Regulation (EC) No 1272/2008 applies the same building blocks with a few divergences: no flammable liquid Category 4, harmonized classifications for many substances in Annex VI, and the Annex V artwork requirement for the pictogram itself. CLP labels for flammables also trigger downstream duties, notably ATEX explosive-atmosphere assessments under Directive 1999/92/EC and the Seveso III thresholds for sites holding large flammable inventories.

What the Flame Does Not Tell You

GHS02 is frequently misread as a generic fire symbol. It is not: it appears only when a substance meets defined classification criteria, so combustible materials that miss the cut-offs — a Category 4 liquid like diesel under CLP, or ordinary combustible solids like wood pellets — legally carry no flame even though they burn. Conversely, the flame on a self-heating substance warns of spontaneous ignition in bulk storage, a hazard invisible to anyone treating the symbol as shorthand for keep away from sparks.

Distinguish GHS02 from its neighbours. GHS03, the flame over a circle, marks oxidizers that intensify fires without necessarily being combustible themselves; storing GHS02 and GHS03 materials together is a classic segregation failure. GHS01 marks detonable materials. In transport, the red Class 3 and Class 2.1 diamonds carry a similar flame, and GHS permits omitting the supply pictogram on outer packaging where the equivalent transport label already appears. Under CLP, when GHS02 is on the label, the GHS04 gas cylinder becomes optional.

Reading the flame pictogram

The flame can communicate flammability, pyrophoricity, self-heating, release of flammable gas, and specified self-reactive, organic peroxide, or desensitized explosive hazards. Not every category in every flammability-related class carries this pictogram.

What to check alongside it

A flame and a flame over a circle communicate different hazards. The latter is the oxidizer pictogram. A flame does not tell you the ignition temperature, suitable extinguishing agent, or complete storage conditions.