A safety data sheet (SDS) is a standardized 16-section document that tells you everything you need to know about a hazardous chemical: what it is, how it can hurt you, and how to protect yourself. Every SDS follows the same structure, mandated by OSHA under the Hazard Communication Standard, so once you learn how to read one, you can read any of them. Here’s how to navigate each part and pull out the information that matters most.
The 16 Sections at a Glance
Every SDS contains the same 16 sections in the same order. You don’t need to memorize all of them, but knowing the layout helps you find critical information fast. Here’s the full list:
- Section 1: Identification (product name, manufacturer, emergency phone number)
- Section 2: Hazard Identification (the most important section for quick safety decisions)
- Section 3: Composition/Ingredients
- Section 4: First-Aid Measures
- Section 5: Fire-Fighting Measures
- Section 6: Accidental Release Measures (spill response)
- Section 7: Handling and Storage
- Section 8: Exposure Controls/Personal Protection
- Section 9: Physical and Chemical Properties
- Section 10: Stability and Reactivity
- Section 11: Toxicological Information
- Section 12: Ecological Information
- Section 13: Disposal Considerations
- Section 14: Transport Information
- Section 15: Regulatory Information
- Section 16: Other Information (including the date the SDS was last updated)
In practice, most workers will spend the bulk of their time in Sections 2, 4, 7, and 8. Those cover hazards, first aid, safe handling, and protective equipment.
Section 2: Hazard Identification
This is the section to read first. It gives you the fastest picture of how dangerous a chemical is and in what way. Three things to look for here: the signal word, the pictograms, and the hazard statements.
Signal Words
There are only two signal words: “Danger” and “Warning.” Danger indicates a more severe hazard, Warning a less severe one. If a chemical has multiple hazards and one qualifies for Danger while another qualifies for Warning, only Danger appears. So when you see that word, take it seriously. It means at least one of the chemical’s hazards falls into a higher severity category.
Pictograms
The red diamond-bordered symbols on an SDS are standardized worldwide. Each one represents a category of hazard:
- Flame: Flammable materials, self-heating chemicals, or substances that emit flammable gas
- Skull and crossbones: Acutely toxic, meaning exposure can be fatal or highly toxic in small amounts
- Health hazard (a person with a starburst on the chest): Long-term health effects like cancer risk, reproductive harm, organ damage, or respiratory sensitization
- Exclamation mark: Lower-level acute hazards like skin or eye irritation, mild toxicity, or drowsiness
- Corrosion: Can cause severe skin burns, serious eye damage, or corrode metals
- Exploding bomb: Explosive or self-reactive
- Flame over circle: Oxidizer, meaning it can intensify a fire by supplying oxygen
- Gas cylinder: Contains gas under pressure, which can explode if heated
- Environment (tree and fish): Toxic to aquatic life (this one is not always required)
Pay attention to the difference between the skull-and-crossbones and the exclamation mark. Both indicate acute toxicity, but the skull means the substance can kill or cause severe poisoning, while the exclamation mark signals a lower level of harm, such as irritation or mild toxic effects.
Hazard Statements
Below the pictograms, you’ll find specific hazard statements in plain language: “Causes severe skin burns and eye damage,” “May cause cancer,” “Highly flammable liquid and vapor.” Read every one. The pictograms tell you the category; the hazard statements tell you exactly what could happen.
Section 3: Identifying the Ingredients
This section lists the chemical ingredients along with their concentrations. The most reliable identifier here is the CAS Registry Number, a unique numerical code assigned to each chemical substance. A single chemical can go by dozens of common names, trade names, or systematic names that vary by region and language. The CAS number cuts through that confusion. If you ever need to look up additional safety information or verify you’re working with the right substance, search by CAS number rather than by name.
Some manufacturers claim trade secret protection for specific ingredients. When they do, the SDS still has to disclose the hazards of those hidden ingredients, even if it doesn’t name them.
Sections 4, 5, and 6: Emergency Response
These three sections cover what to do when something goes wrong. Section 4 organizes first-aid instructions by route of exposure: inhalation, skin contact, eye contact, and ingestion. Each route has its own set of steps because the correct response differs dramatically. Flushing eyes with water is the right call for a chemical splash; inducing vomiting after swallowing a corrosive substance can cause more damage. The section also lists symptoms you might experience after exposure, which helps you recognize a problem even if you didn’t notice the initial contact.
Section 5 covers fire-fighting measures, including which types of extinguishing agents work on that particular chemical and which ones could make things worse. Some chemicals react violently with water, for instance, so using a standard water extinguisher could be dangerous.
Section 6 addresses spills and accidental releases. It outlines containment methods, cleanup techniques, and personal precautions you should take before approaching a spill. If you work somewhere a spill is plausible, familiarize yourself with this section before an incident happens, not during one.
Sections 7 and 8: Daily Handling and Protection
If you work with a chemical regularly, these two sections are the ones that affect your day-to-day routine. Section 7 covers safe handling practices and storage conditions. It tells you things like whether a chemical needs to be kept away from heat sources, stored in a ventilated area, or separated from incompatible materials. Ignoring storage incompatibilities is one of the most common causes of workplace chemical incidents.
Section 8 is where you find out what personal protective equipment (PPE) to use. A well-written SDS will specify the type of gloves (nitrile vs. latex vs. butyl rubber, for example), the kind of eye protection needed (safety glasses vs. chemical splash goggles vs. a face shield), and whether you need respiratory protection. It also lists occupational exposure limits, which are the maximum concentrations of a chemical you can safely breathe over a work shift. If your workplace exposure approaches those limits, engineering controls like fume hoods or ventilation systems should be in place in addition to PPE.
Section 9: Physical and Chemical Properties
This section reads like a data table, and most of it is technical. But a few values are worth understanding. The flash point is the lowest temperature at which a chemical’s vapors can ignite. A low flash point means the substance can catch fire at or near room temperature, which changes how you store and handle it. Vapor pressure tells you how quickly a liquid evaporates. High vapor pressure means fumes build up fast in enclosed spaces, increasing both inhalation risk and fire risk. Other properties listed include appearance, odor, pH, boiling point, and solubility in water.
Section 11: How Toxic Is It?
This section quantifies a chemical’s toxicity using standardized measurements. The most common is the LD50, which stands for the dose lethal to 50% of test animals. A lower number means a more toxic substance. For example, a chemical with an oral LD50 below 50 mg/kg is classified as highly acutely toxic, while one with an LD50 of several thousand mg/kg poses much less acute danger.
For inhaled chemicals, you’ll see an LC50 instead, which measures the airborne concentration that’s lethal to half of test animals. Values below 200 ppm flag a substance as highly toxic by inhalation.
Section 11 also tells you whether a substance is classified as a carcinogen, whether it causes reproductive harm, and which organs it targets with repeated exposure. These long-term hazard details matter just as much as the acute toxicity numbers, especially if you work with the chemical frequently.
Sections 12 Through 16: Disposal, Transport, and Regulations
The final five sections are less relevant to daily handling but still important in specific situations. Section 12 covers environmental impact, including whether a chemical is toxic to aquatic life or accumulates in ecosystems. Section 13 provides disposal guidance, which prevents you from pouring something down a drain that could contaminate water supplies or react with other waste. Section 14 gives shipping classifications, including the UN identification number and hazard class needed for safe transport. Section 15 lists any additional regulations that apply to the product. Section 16 notes the date the SDS was last revised, which tells you whether you’re looking at current information or an outdated document.
Your Right to Access an SDS
Under OSHA’s Hazard Communication Standard, your employer is required to keep an SDS for every hazardous chemical in the workplace and make it immediately accessible to you during your shift. This can be a physical binder, a digital system, or any other format, as long as there are no barriers to getting the information when you need it. Your employer is also required to train you on how to read and use these sheets when you start a job and whenever a new chemical hazard is introduced to your work area.
OSHA recently updated the Hazard Communication Standard to align with newer international classification criteria. Manufacturers of single-ingredient chemicals must comply with the updated rules by January 2026, and employers need to update their training and labeling for those substances by mid-2026. Mixtures have a longer timeline, with employer compliance required by May 2028. If you notice your workplace SDS sheets haven’t been updated in years, that’s worth flagging, since outdated sheets may be missing hazard information that newer classifications now require.