A hazard statement is a standardized phrase that describes the nature and severity of a chemical’s danger. “Fatal if swallowed,” “Causes severe skin burns and eye damage,” and “Very toxic to aquatic life” are all examples. These statements appear on chemical labels and Safety Data Sheets (SDS) so that anyone handling, storing, or transporting a chemical knows exactly what risks it poses.
Hazard statements are part of the Globally Harmonized System of Classification and Labelling of Chemicals (GHS), an international framework now in its 11th revision as of 2025. In the United States, OSHA’s Hazard Communication Standard requires them on every hazardous chemical in the workplace.
How the H-Code System Works
Every hazard statement is assigned a unique code starting with the letter “H” followed by three numbers. That code isn’t random. The first digit after the H tells you which broad category of hazard you’re dealing with:
- H2xx (200 series): Physical hazards, such as explosivity, flammability, or oxidizing properties
- H3xx (300 series): Health hazards, such as toxicity, skin corrosion, or cancer risk
- H4xx (400 series): Environmental hazards, such as aquatic toxicity
The last two digits correspond to the specific type of hazard within that category. For physical hazards, codes from 200 to 210 relate to explosivity, while codes from 220 to 230 relate to flammability. So if you see H224 on a label, you immediately know it’s a physical hazard (the “2”) related to flammability (the “24” falls in the 220–230 range). The actual statement for H224 is “Extremely flammable liquid and vapour.”
What Hazard Statements Sound Like
Hazard statements follow a deliberate phrasing pattern. They’re short, direct descriptions of what the chemical can do. They also scale in severity. For oral toxicity, for example, the statements range across categories:
- H300: Fatal if swallowed
- H301: Toxic if swallowed
- H302: Harmful if swallowed
Notice how the language shifts from “fatal” to “toxic” to “harmful.” Each version corresponds to a different hazard category based on how much of the substance it takes to cause harm. The same scaling pattern appears for skin contact, inhalation, and other exposure routes. A chemical can carry multiple hazard statements if it poses more than one type of risk.
Hazard Statements vs. Precautionary Statements
These two types of statements serve different purposes and are easy to confuse. A hazard statement tells you what the danger is. A precautionary statement tells you what to do about it. Hazard statements start with H codes; precautionary statements start with P codes.
“Fatal if swallowed” is a hazard statement. “Do not eat, drink or smoke when using this product” is a precautionary statement. Both appear on the same label, but they answer different questions. One describes the risk, the other describes the protective action.
Where You’ll Find Them
Hazard statements are required in two places: on the chemical’s label and in Section 2 of its Safety Data Sheet. Section 2, titled “Hazard(s) Identification,” is where all the warning information lives. It must include the hazard classification, the signal word, all applicable hazard statements, pictograms, precautionary statements, and a description of any hazards that don’t fit the standard categories.
On a label, the hazard statement sits alongside several other elements that work together to communicate risk at a glance. A signal word tells you the overall severity: “Danger” is used for the most severe hazards, and “Warning” for less severe ones. Pictograms, those red-bordered diamond symbols, give you a visual cue. A skull and crossbones pairs with acute toxicity statements like H300. A corrosion pictogram pairs with statements about skin burns. The environment pictogram (a dead tree and fish) appears alongside aquatic toxicity statements like H400.
Why the Standardization Matters
Before the GHS, different countries used completely different systems to label the same chemical. A substance shipped from one country to another might arrive with hazard information in a format that workers at the receiving end couldn’t interpret. The GHS, and by extension the standardized hazard statement system, solved this by creating a single vocabulary. Whether you’re reading a label in a warehouse in Texas or a factory in Germany, H301 means the same thing: “Toxic if swallowed.”
OSHA adopted this system through its 2012 update to the Hazard Communication Standard, aligning U.S. workplaces with international practice. The result is that every hazard statement you encounter on a chemical product in the U.S. follows the same coding and phrasing used globally. If you can read one GHS label, you can read any of them.
Reading Hazard Statements in Practice
When you pick up a chemical product and look at the label, start with the signal word to gauge overall severity. Then read each hazard statement to understand the specific risks. A single product might carry H225 (“Highly flammable liquid and vapour”), H319 (“Causes serious eye irritation”), and H336 (“May cause drowsiness or dizziness”) all at once. Each one tells you something different about how the product can hurt you and through what route.
Pay attention to the verb. “Causes” means the effect is well established. “May cause” introduces some uncertainty, typically because the evidence is strong but the effect doesn’t happen in every case or depends on conditions. The wording is chosen carefully and reflects how much scientific evidence supports the hazard at a given severity level.
If you want the full picture, pull up the product’s Safety Data Sheet and go to Section 2. It will list every hazard statement along with the hazard classification and category that generated it, giving you more context than the label alone provides.