GHS Signal Words

GHS Signal Words

Quick Reference Guide to Understanding GHS Signal Words and Their Severity

Signal words are a required part of every GHS-compliant chemical label. Their purpose is straightforward: they tell workers how serious a hazard is, immediately and at a glance. While pictograms and hazard statements describe the type of hazard, the signal word communicates the overall severity based on the chemical’s official GHS classifications.


In U.S. workplaces, OSHA incorporates signal word requirements through the Hazard Communication Standard (HCS), 29 CFR 1910.1200. Every shipped container label and every SDS must display the correct signal word exactly as assigned by the manufacturer or importer.


Understanding signal words helps workers recognize risk levels quickly and helps employers ensure that workplace labels and training remain fully compliant.

The Two GHS Signal Words Used

Under the Globally Harmonized System, there are only two approved signal words: Danger and Warning. These words provide a quick indication of how severe a chemical’s hazards are based on its official classification. A label will display either one of these signal words or, in some cases, none at all if the assigned hazard categories do not require one. You will never see both signal words on the same label.


Signal words are not selected by preference. They are assigned directly from the chemical’s GHS hazard classes and categories according to strict criteria. This ensures that every supplier communicates hazard severity consistently, allowing workers to quickly recognize and respond to the level of risk.

What “Warning” Means on a GHS Label

Warning indicates that the chemical presents hazards, but at a lower severity than those that require “Danger.” These hazards can still cause injury, illness, or environmental impact if handled incorrectly, and they still require proper PPE, safe handling, and employee training.

Typical hazards that trigger “Warning":

  • Skin and eye irritation

  • Flammable liquids (Category 3)

  • Acute toxicity (Category 4)

  • Narcotic effects such as dizziness (STOT SE Category 3)

Workers should understand that “Warning” does not mean low risk. It simply tells them the hazards fall into lesser severity categories compared to those that require “Danger.”

When “Warning” Appears

  • Skin and eye irritation

  • Flammable liquids (Category 3)

  • Acute toxicity (Category 4)

  • Narcotic effects such as dizziness (STOT SE Category 3)

Workers should understand that “Warning” does not mean low risk. It simply tells them the hazards fall into lesser severity categories compared to those that require “Danger.”

What “Danger” Means on a GHS Label

Danger is the strongest signal word under GHS and is used only for chemicals with the highest-severity hazard categories. These hazards are more likely to cause severe injury, permanent damage, or life-threatening outcomes.

Hazard types commonly associated with “Danger”:

  • Severe acute toxicity (Category 1 or 2)

  • Skin corrosion (Category 1)

  • Serious eye damage (Category 1)

  • Pyrophoric substances

  • Carcinogens, mutagens, and reproductive toxins (Category 1)

  • Specific organ toxicity (Category 1)

A “Danger” signal word alerts workers that the chemical demands heightened caution, stricter handling procedures, and appropriate PPE without exception.

When “Danger” Appears

A label must display Danger when:


  • Any hazard category assigned to the chemical requires it

  • The SDS identifies “Danger” as the signal word

  • One or more hazards fall into the highest severity classifications

Once “Danger” is triggered, “Warning” cannot appear anywhere on the label.

Why Some Chemicals Have No Signal Word

A chemical may have no signal word and still present hazards. This occurs when its assigned GHS hazard categories do not require a signal word or when the only hazards fall under classifications not adopted by OSHA, such as most environmental hazards. Some hazard types, like combustible dust, also fall outside the GHS categories that use signal words.


Even without a signal word, the label and SDS will still include hazard statements and pictograms, which workers should use to understand the level of risk. No signal word never means the product is safe; it simply means none of the adopted hazard categories trigger one.

How Signal Words Work When There Are Multiple Hazards

Many chemicals are classified under multiple hazard classes, which can result in both high-severity and lower-severity hazards. OSHA provides a simple rule: Use only the signal word for the highest hazard severity.


If even one hazard category requires Danger, that becomes the only signal word on the label. When all hazards fall within lower-severity thresholds, the label will display Warning. If no adopted hazard category requires either, the label will display none. This approach ensures workers immediately recognize the most serious hazard associated with the product.

Where to Find Signal Words on the Label

Workers and safety managers can confirm the correct signal word in two places.


The first is Section 2 of the Safety Data Sheet (SDS), which lists the chemical’s hazard classifications and includes the assigned signal word along with hazard statements and pictograms. This is the authoritative reference for any workplace or secondary container labeling.


The second location is the shipped container label, where the signal word appears prominently near the product identifier and pictograms for quick visibility. Any workplace label created by employers must use the exact same signal word shown on the SDS or shipped label, without alteration.

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