GHS Hazard Classification Explained: Pictograms, Signal Words, and H-Codes

What is GHS?

The Globally Harmonized System of Classification and Labelling of Chemicals (GHS) is an internationally agreed-upon system for classifying chemicals based on their hazards. The United States adopted GHS through OSHA's revised Hazard Communication Standard (HazCom 2012).

GHS provides a universal language for chemical hazards so that workers, emergency responders, and consumers worldwide can understand the risks of any chemical product at a glance.

GHS Pictograms

GHS uses nine standardized pictograms — red diamond-shaped symbols on a white background — to communicate hazard types:

Health Hazards

• Skull and Crossbones (GHS06) — Acute toxicity (fatal or toxic if swallowed, inhaled, or through skin contact)
• Health Hazard (GHS08) — Serious health effects including carcinogenicity, respiratory sensitization, reproductive toxicity, organ damage
• Exclamation Mark (GHS07) — Irritation, skin sensitization, acute toxicity (harmful), narcotic effects

Physical Hazards

• Flame (GHS02) — Flammable gases, liquids, solids, aerosols; self-reactive substances
• Flame Over Circle (GHS03) — Oxidizers that may cause or intensify fire
• Exploding Bomb (GHS01) — Explosives, self-reactive substances, organic peroxides
• Gas Cylinder (GHS04) — Gases under pressure
• Corrosion (GHS05) — Corrosive to metals; causes severe skin burns and eye damage

Environmental Hazards

• Environment (GHS09) — Hazardous to the aquatic environment

Signal Words

Every GHS-classified chemical is assigned one of two signal words:

• Danger — Used for more severe hazard categories. If you see "Danger," the chemical poses serious risks and requires strict handling precautions.
• Warning — Used for less severe hazard categories. Still hazardous, but lower risk than "Danger" chemicals.

A chemical can only have one signal word. If it qualifies for both, "Danger" takes precedence.

Hazard Statements (H-Codes)

Hazard statements are standardized phrases describing the nature of the hazard. They use an "H" prefix followed by a three-digit number:

Physical Hazard Statements (H200–H290)

• H220 — Extremely flammable gas
• H225 — Highly flammable liquid and vapour
• H226 — Flammable liquid and vapour
• H271 — May cause fire or explosion; strong oxidiser
• H280 — Contains gas under pressure; may explode if heated

Health Hazard Statements (H300–H373)

• H300 — Fatal if swallowed
• H301 — Toxic if swallowed
• H302 — Harmful if swallowed
• H310 — Fatal in contact with skin
• H314 — Causes severe skin burns and eye damage
• H315 — Causes skin irritation
• H317 — May cause an allergic skin reaction
• H318 — Causes serious eye damage
• H330 — Fatal if inhaled
• H332 — Harmful if inhaled
• H334 — May cause allergy or asthma symptoms if inhaled
• H340 — May cause genetic defects
• H350 — May cause cancer
• H360 — May damage fertility or the unborn child
• H370 — Causes damage to organs
• H372 — Causes damage to organs through prolonged exposure

Environmental Hazard Statements (H400–H420)

• H400 — Very toxic to aquatic life
• H410 — Very toxic to aquatic life with long lasting effects
• H411 — Toxic to aquatic life with long lasting effects

Precautionary Statements (P-Codes)

Precautionary statements tell you how to safely handle, store, and dispose of the chemical. They use a "P" prefix:

• P2xx — Prevention (e.g., P210: Keep away from heat, sparks, open flames)
• P3xx — Response (e.g., P301+P310: IF SWALLOWED: Immediately call a POISON CENTER)
• P4xx — Storage (e.g., P403: Store in a well-ventilated place)
• P5xx — Disposal (e.g., P501: Dispose of contents/container in accordance with local regulations)

Reading a GHS Label

A compliant GHS label contains:

1. Product identifier — Chemical name or product name
2. Signal word — Danger or Warning
3. Pictogram(s) — Applicable red diamond symbols
4. Hazard statements — All applicable H-codes
5. Precautionary statements — Relevant P-codes
6. Supplier information — Name, address, phone number

Why GHS Matters for Your Workplace

Understanding GHS classification helps you:

• Quickly assess risks when receiving new chemicals
• Select proper PPE based on hazard types
• Store chemicals safely by understanding incompatibilities
• Respond to emergencies with the right first aid measures
• Train employees effectively using universal hazard communication