A Safety Data Sheet (SDS) is a standardized document that tells you everything you need to know about a hazardous chemical: what it can do to you, how to protect yourself, and what to do if something goes wrong. Every SDS follows the same 16-section format required by OSHA’s Hazard Communication Standard, which means once you learn how to read one, you can read them all. The key is knowing which sections matter most for your situation and how to interpret what you find there.
The 16-Section Layout
Every SDS uses the same structure, adopted from the Globally Harmonized System (GHS) of chemical classification. Before 2016, these documents were called Material Safety Data Sheets (MSDSs) and could vary wildly in format from one manufacturer to another. The current standardized layout makes it far easier to find what you need quickly.
Here’s the full list:
- Section 1: Identification (product name, manufacturer, emergency phone number)
- Section 2: Hazard Identification (the most critical safety summary)
- Section 3: Composition/Information on Ingredients
- Section 4: First-Aid Measures
- Section 5: Fire-Fighting Measures
- Section 6: Accidental Release Measures (spill cleanup)
- 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
You don’t need to memorize all 16 sections. In practice, the sections you’ll return to most often are 2, 4, 7, 8, and 10. Those cover the hazards, first aid, how to handle and store the chemical, what protective equipment you need, and what the chemical reacts badly with.
Section 2: Hazard Identification
This is the single most important section on the sheet. It gives you a quick snapshot of every danger the chemical poses, using three tools: pictograms, signal words, and hazard statements.
Pictograms
You’ll see one or more red-bordered diamond symbols. Each one represents a category of danger:
- Flame: The chemical is flammable, self-heating, or releases flammable gas.
- Flame over circle: It’s an oxidizer, meaning it can intensify a fire by feeding it oxygen.
- Exploding bomb: Explosive or capable of violent self-reaction.
- Gas cylinder: Contents are under pressure and can rupture or explode.
- Corrosion: Causes skin burns, serious eye damage, or corrodes metals.
- Skull and crossbones: Can be fatal or toxic with a single exposure.
- Health hazard (person with star on chest): Long-term health effects like cancer, reproductive harm, organ damage, or respiratory sensitization.
- Exclamation mark: Less severe hazards like skin or eye irritation, allergic skin reactions, or drowsiness.
- Environment (dead tree and fish): Toxic to aquatic life. This pictogram is not always required.
Pay close attention to the difference between the skull and crossbones and the exclamation mark. Both relate to toxicity, but the skull means the substance can kill or seriously poison you in a single dose. The exclamation mark indicates a lower level of harm, like irritation or nausea.
Signal Words
There are only two: “Danger” and “Warning.” Danger indicates the more severe hazard. Warning indicates a less severe one. If a chemical has multiple hazards and some qualify for Danger while others qualify for Warning, only Danger will appear. So when you see Danger on a sheet, treat the chemical with extra caution.
H-Codes and P-Codes
Section 2 also lists hazard statements (H-codes) and precautionary statements (P-codes). H-codes describe the specific nature of the danger in plain language, like “Causes serious eye damage” or “May cause cancer.” P-codes tell you what to do about it: prevention steps, response actions, storage conditions, and disposal instructions. Reading the H-codes first gives you the clearest picture of what the chemical can actually do to you.
Section 8: Exposure Limits and Protective Equipment
This section tells you two things: how much exposure is considered safe and what gear you need to stay within those limits.
You’ll see exposure limits listed as abbreviations. The most common ones are PEL (Permissible Exposure Limit, set by OSHA) and REL (Recommended Exposure Limit, set by NIOSH). Both are usually expressed as a TWA, or time-weighted average. This is the average concentration of the chemical in the air you can be exposed to over a full work shift (8 hours for OSHA, 10 hours for NIOSH) without expected harm. Some chemicals also list a STEL, or short-term exposure limit, which is the maximum concentration allowed over any 15-minute window during the day.
If you’re not doing air monitoring, these numbers still matter. A very low exposure limit tells you the substance is potent and that even small amounts in the air are a concern. That context helps you understand why a full respirator might be required instead of just a simple dust mask. Below the exposure limits, Section 8 specifies the personal protective equipment you need: glove type, eye protection, respiratory protection, and body coverings. Follow these recommendations exactly as listed for the specific chemical you’re working with.
Section 9: Physical and Chemical Properties
This section lists measurable characteristics of the chemical. Not all of them will matter to you, but a few are worth understanding:
- Flash point: The lowest temperature at which the chemical gives off enough vapor to ignite. A low flash point (below room temperature) means the substance can catch fire easily under normal conditions.
- pH: Tells you how acidic or alkaline the substance is. Extreme values in either direction (below 2 or above 12) typically mean severe corrosion risk to skin and metals.
- Vapor pressure: Indicates how quickly the chemical evaporates. High vapor pressure means fumes build up fast in enclosed spaces, increasing inhalation risk.
- Boiling point: Helps you understand at what temperatures the chemical becomes a vapor hazard.
- Appearance and odor: Useful for identifying leaks or spills. Some entries include an odor threshold, the concentration at which you can actually smell it. If the odor threshold is higher than the exposure limit, you can be overexposed before you even notice.
Not every SDS will have data for all properties. When information is unavailable, the sheet will note that explicitly rather than leave a blank.
Section 10: Stability and Reactivity
This section tells you what can make the chemical dangerous beyond its baseline hazards. It covers conditions to avoid (heat, sparks, sunlight, moisture, static discharge), incompatible materials, and what hazardous byproducts the chemical produces when it breaks down.
The incompatible materials list is especially important for storage. A base stored next to a strong acid, or an oxidizer stored near flammable materials, can cause violent reactions. Section 10 will name specific classes of chemicals to keep separated, like “avoid storage with strong acids” or “keep away from air or oxygen.” If you’re responsible for organizing a chemical storage area, this is the section you need to cross-reference for every product on the shelf.
Section 4: First-Aid Measures
This section breaks down emergency response by the four routes of exposure: inhalation (breathing it in), skin contact, eye contact, and ingestion (swallowing). For each route, the SDS describes specific first-aid steps and the symptoms you should watch for, both immediately after exposure and potentially delayed effects.
Read this section before you work with the chemical, not after an accident. Knowing in advance that a particular substance requires 15 minutes of continuous eye flushing, or that skin contact requires removing contaminated clothing immediately, saves critical time during an emergency. Some SDSs also note whether the chemical’s effects are delayed, meaning you might feel fine initially but develop symptoms hours later.
Sections 5, 6, and 7: Fire, Spills, and Daily Handling
Section 5 covers fire-fighting measures: what type of extinguisher to use (water, foam, dry chemical, CO2) and which methods to avoid. Some chemicals react violently with water, making a standard fire extinguisher the wrong choice. This section also lists hazardous combustion products, the toxic gases or fumes released when the chemical burns.
Section 6 covers spill response. It describes containment and cleanup methods, what materials to use for absorption, and what personal protection you need during cleanup. For a small lab spill versus a large industrial release, the instructions may differ.
Section 7 tells you how to handle and store the chemical day to day. This includes ventilation requirements, temperature ranges for storage, humidity considerations, and whether the container needs to be grounded to prevent static discharge. It also notes whether the chemical needs to be kept away from certain materials during storage, which ties back to the incompatibility information in Section 10.
Section 11: Toxicological Information
This section provides detailed data on the health effects of the chemical. You’ll often see a value called LD50, which stands for “lethal dose 50%.” This is the estimated amount of the substance that killed 50% of test animals in laboratory studies. A lower LD50 means a smaller amount is needed to cause death, which means the substance is more toxic. You may also see LC50, which is the same concept but for inhaled concentrations rather than ingested doses.
Beyond the lethal dose data, Section 11 describes whether the chemical causes cancer, genetic damage, reproductive harm, or organ damage with repeated exposure. These long-term effects correspond to the health hazard pictogram (the silhouette with a star on the chest) from Section 2. If you’re working with a chemical regularly over weeks or months, this section helps you understand the cumulative risks beyond a single exposure incident.
Sections 12 Through 16
The remaining sections are primarily relevant to environmental safety, waste disposal, and shipping. Section 12 covers ecological toxicity, including harm to aquatic life. Sections 13 and 14 address disposal methods and transportation classification. Section 15 lists applicable regulations, and Section 16 contains any additional notes, including the date the SDS was last revised.
OSHA requires Sections 12 through 15 to be present on the sheet, but the content in those sections falls under the jurisdiction of other agencies like the EPA and the Department of Transportation. For most workers, these sections come into play only when you’re disposing of chemicals, shipping them, or conducting an environmental review. The revision date in Section 16 is worth checking. OSHA’s 2024 update to the Hazard Communication Standard, aligning with the seventh revision of the GHS, means newer SDSs may contain updated hazard classifications or labeling. If your SDS is several years old, request a current version from the manufacturer.