GHS / HazCom term · Glossary
Signal Word
Verified vs OSHA sources · 2026-10-05
A single standardized word on a GHS label that signals the relative severity of a chemical's hazard. GHS uses only two — “Danger” for more severe hazards and “Warning” for less severe ones. Only one signal word appears on a label: “Danger” if any hazard class on the product warrants it.
Also known as: GHS signal word
Signal Word at a glance
- Only two signal words exist: “Danger” (severe) and “Warning” (less severe).
- Just one signal word per label — “Danger” takes precedence over “Warning.”
- Assigned by hazard class and category, not chosen at will.
- One of the six required GHS label elements under 1910.1200(f).
In plain English
The one word at the top of a chemical label that tells you how bad the hazard is. “Danger” = more serious; “Warning” = less serious. There's never more than one — if anything on the label rates “Danger,” that's the word used.
What the rule says
“Signal word means a word used to indicate the relative level of severity of hazard and alert the reader to a potential hazard on the label. The signal words used in this section are “danger” and “warning.” “Danger” is used for the more severe hazards, while “warning” is used for the less severe.”
In context
A classification or labeling concept from the UN Globally Harmonized System, adopted into US law through OSHA's Hazard Communication Standard (29 CFR 1910.1200) and its appendices.
Where this is written in OSHA's rules
- 29 CFR 1910.1200(c)Read on eCFR / OSHA.gov
Example
A flammable liquid in Category 1 or 2 is assigned the signal word “Danger.” A Category 3 flammable liquid is assigned “Warning.” If a product is both a Category 2 flammable (Danger) and a mild eye irritant (Warning), only “Danger” appears — the more severe word wins.
Why it matters
The signal word is the quickest severity cue on a label, and it must match the chemical's classification. Using “Warning” where “Danger” is required — or printing both — understates the hazard to workers and is a HazCom labeling violation under 1910.1200(f).
“Danger” vs. “Warning” — and why only one
They are not interchangeable: “Danger” is reserved for the more severe hazard categories, “Warning” for the less severe. A label never shows both — if any hazard on the product calls for “Danger,” that single word is used and “Warning” is dropped.
GHS signal words
| Signal word | Severity | Typical example |
|---|---|---|
| Danger | More severe hazard categories | Flammable liquid Cat 1–2; acute toxicity Cat 1–3 |
| Warning | Less severe hazard categories | Flammable liquid Cat 3; mild skin/eye irritation |
| (none) | Not severe enough to warrant one | Some lowest-tier hazard categories |
Signal Word: frequently asked questions
- What are the two GHS signal words?
- “Danger” and “Warning.” “Danger” is used for the more severe hazards and “Warning” for the less severe. A label carries only one of them.
- Can a label have both 'Danger' and 'Warning'?
- No. Only one signal word appears per label. If the product has any hazard that requires “Danger,” that word is used and “Warning” is not shown.
- Who decides which signal word to use?
- It's set by the chemical's GHS hazard classification — each hazard class and category is assigned a specific signal word in the GHS criteria, not chosen at the label-writer's discretion.
Related terms
Free tools for this
Governing OSHA standards
More GHS terms
A GHS health-hazard class for the harmful effects that follow a single dose, several doses within 24 hours, or a 4-hour inhalation exposure. Chemicals are sorted into categories by route (oral, dermal, inhalation) using LD50/LC50 cut-offs — Category 1 is the most toxic. OSHA's HazCom standard uses Categories 1–4.
Aspiration HazardA GHS health-hazard class for chemicals that can be fatal if swallowed and then enter the airways — directly or by vomiting — causing chemical pneumonia or lung injury. Thin, low-viscosity hydrocarbons (gasoline, kerosene, lamp oil) are the classic example. It is Category 1, with the health-hazard pictogram (GHS08) and signal word “Danger.”
CarcinogenicityA GHS health-hazard class for chemicals that cause cancer or increase its incidence. GHS (and OSHA's HazCom standard) sorts carcinogens into Category 1A (known human carcinogen), 1B (presumed, from animal evidence), and Category 2 (suspected). Carcinogens carry the health-hazard pictogram (GHS08) and a hazard statement such as H350 (“May cause cancer”).
Chemicals Under PressureA physical-hazard class added by OSHA's 2024 HCS update (aligning with GHS Revision 7) for liquids or solids pressurized with a gas, held in pressure receptacles other than aerosol dispensers and not classified as gases under pressure. It is categorized by the flammability of its contents and always carries the gas-cylinder pictogram (GHS04) for the pressure hazard.
ClassificationThe process of evaluating the available scientific evidence for a chemical against the GHS criteria to decide whether it is hazardous and, if so, the hazard class and category of each effect. Classification is the first step in HazCom — its result determines every label element (pictogram, signal word, hazard and precautionary statements) and SDS content.
Corrosive to MetalsA GHS physical-hazard class for chemicals that, by chemical action, will materially damage or even destroy metals. It is a single category (Category 1), determined by corrosion-rate testing on steel and aluminum, and uses the corrosion pictogram (GHS05) with the hazard statement H290. It is a separate hazard from skin corrosion, even though both use GHS05.
Desensitized ExplosivesA physical-hazard class added by OSHA's 2024 HCS update (GHS Revision 7) for solid or liquid explosives that have been phlegmatized — wetted or diluted — to suppress their explosive properties for safe transport and storage. It has four categories based on the corrected burning rate, and uses the flame pictogram (GHS02), not the exploding-bomb.
Globally Harmonized System (GHS)An internationally agreed framework created by the United Nations (first adopted in 2003) that standardizes how chemical hazards are classified and communicated — using common hazard classes, pictograms, signal words (Danger / Warning), and coded hazard (H) and precautionary (P) statements on labels and safety data sheets. The US adopted GHS into law through OSHA's 2012 Hazard Communication Standard update.
Sources & verification
- 29 CFR 1910.1200(c) (eCFR / OSHA.gov)
- OSHA — Hazard Communication (labels)
- OSHA Brief — Hazard Communication Standard: Labels and Pictograms (OSHA 3636)
Reviewed by HazComFast against eCFR, OSHA.gov, NIOSH, and the Federal Register. Last reviewed 2026-10-05. This glossary is general information, not legal advice; OSHA State-Plan states (e.g. California, Michigan) may adopt stricter requirements.
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