Oxidizer

What the Flame Over Circle Identifies

GHS03 — a flame burning above a circle — is reserved for three hazard classes: oxidizing gases (Category 1), oxidizing liquids (Categories 1 to 3), and oxidizing solids (Categories 1 to 3). These are materials that supply oxygen or otherwise support combustion, so they can cause or intensify a fire in surrounding material even when they cannot burn themselves. Oxygen, concentrated hydrogen peroxide, nitric acid above certain concentrations, ammonium nitrate, calcium hypochlorite, and potassium permanganate are typical carriers of this pictogram.

The circle in the artwork represents an oxygen source feeding the flame, which captures the operational problem precisely: an oxidizer defeats the fire-prevention logic that most workplaces rely on. Removing ignition sources is not enough, because oxidizers can ignite combustibles on contact, and fires involving them burn hotter, spread faster, and resist smothering. Some incidents, such as pool-chemical warehouse fires involving hypochlorites, start with nothing more exotic than contamination by organic material.

Categories, Signal Words, and Hazard Statements

Oxidizing gases have a single category, signal word Danger, and H270 (may cause or intensify fire; oxidiser). Oxidizing liquids and solids split into three categories by test performance: Category 1 takes Danger with H271 (may cause fire or explosion; strong oxidiser), Category 2 takes Danger with H272 (may intensify fire; oxidiser), and Category 3 takes Warning with the same H272 statement. All six assignments display GHS03; the category changes only the signal word and statement, not the pictogram.

Classification rests on comparative burning tests from the UN Manual of Tests and Criteria: candidate liquids and solids are mixed with cellulose and their burning behavior compared against reference oxidizers. This matters for mixtures and dilutions — hydrogen peroxide at 60 percent is a markedly different classification case than at 8 percent — so the same chemical name can appear with or without GHS03 depending on concentration. The label on the specific container, not the substance name, is the authoritative signal.

OSHA HazCom, EU CLP, and Storage Consequences

OSHA's Hazard Communication Standard (29 CFR 1910.1200) requires GHS03 on shipped containers of classified oxidizers, and the classification connects to NFPA 400 and fire-code storage requirements: maximum allowable quantities, segregation distances, and sprinkler design all key off the oxidizer class. Under the EU CLP Regulation (EC) No 1272/2008, the same pictogram applies, with Annex VI providing harmonized classifications for common oxidizers and the Seveso III Directive imposing site-level duties once oxidizer inventories cross tonnage thresholds.

The single most important control the pictogram should trigger is segregation. Oxidizers must be stored apart from flammable and combustible materials, reducing agents, and organic matter — including incidental combustibles such as wooden pallets, cardboard, and spilled oils. Housekeeping is a real control here: a GHS03-labeled drum standing on an oil-stained wooden pallet is an ignition scenario, not just poor practice. Spill response also changes, because absorbing an oxidizer into sawdust or standard organic absorbent can start the fire the label warns about.

Common Confusions Around GHS03

The flame over circle is routinely confused with the plain GHS02 flame. The difference is causal direction: GHS02 materials burn; GHS03 materials make other things burn. Some substances genuinely warrant related pictograms — certain organic peroxides have both oxidizing and self-reactive character but are classified in the organic peroxides class, which assigns GHS01 or GHS02 rather than GHS03. If GHS01 already appears on a label, GHS and CLP make GHS03 optional in most cases to avoid redundant symbols.

In transport, oxidizers travel as Class 5.1 under a yellow diamond bearing the same flame-over-circle symbol, and oxygen cylinders carry the oxidizer label alongside the non-flammable gas Class 2.2 label. GHS allows outer packagings already bearing the transport oxidizer diamond to omit the duplicate supply pictogram. One further trap: oxidizing does not mean corrosive, and vice versa — nitric acid earns both GHS03 and GHS05, but sodium hypochlorite bleach at household strength is typically labeled corrosive or irritant without any oxidizer pictogram.

Reading the flame over circle pictogram

The flame over a circle identifies oxidizing hazards in applicable gas, liquid, and solid classifications. An oxidizer can cause or intensify combustion; this is different from saying that the substance itself is flammable.

What to check alongside it

Do not substitute the ordinary flame pictogram. Use the product label and safety data sheet to establish incompatible materials and handling conditions.