How to Read a Safety Data Sheet: All 16 GHS Sections Explained

Every hazardous chemical in a workplace comes with a safety data sheet. Under OSHA’s Hazard Communication Standard (29 CFR 1910.1200), manufacturers and importers must provide an SDS for every chemical they sell that meets the definition of hazardous, and employers must keep those documents accessible to workers. That’s the rule. What actually matters is whether workers and safety professionals know how to use them.

The GHS format standardized safety data sheets into 16 sections in a fixed order. That fixed structure is the whole point. A worker dealing with a chemical spill doesn’t have time to scan through a 10-page document. Knowing that first aid is always in Section 4 and spill response is always in Section 6 cuts that search to seconds.

The 16 Sections and What to Look For

Section 1: Identification

This is the product name, manufacturer name, contact information, and emergency phone number. The emergency number is the one to verify first. Some manufacturers list a 24-hour emergency response line through CHEMTREC or a similar service. Others list a business hours number that won’t help at 11pm. If your facility uses high-hazard chemicals, confirm the emergency numbers before you need them.

The intended use section tells you what the chemical is meant to do. Uses not listed there are off-label. That matters for your hazard assessment.

Section 2: Hazard Identification

This is the most important section for a quick hazard assessment. It contains the GHS hazard classification, the signal word (Danger or Warning), hazard statements, precautionary statements, and the GHS pictograms.

The nine GHS pictograms cover:

Flame (flammable), Flame over circle (oxidizer), Exploding bomb (explosive or reactive), Corrosion (skin/eye corrosive), Skull and crossbones (acute toxicity), Exclamation mark (irritant, less severe), Health hazard (carcinogen, reproductive toxicant, sensitizer, target organ toxicant), Environment (aquatic toxicity), and Gas cylinder (compressed gas).

A chemical can have multiple pictograms. A solvent might show flame and exclamation mark and health hazard. Read all of them. The signal word tells you relative severity but doesn’t replace reading the actual hazard statements.

Section 3: Composition and Ingredients

What’s in the product, by CAS number and concentration range. This matters for three reasons.

First, mixtures don’t always behave like their components. A product can contain a hazardous ingredient at a concentration below the GHS classification threshold and still pose a workplace exposure risk at the levels you’re actually using it.

Second, some ingredients are listed as “proprietary.” Manufacturers can withhold exact formulas under trade secret claims. But OSHA requires them to disclose hazardous ingredients even in proprietary formulas if exposure limits exist. If an SDS lists a major component as “proprietary,” that’s a red flag. Push the manufacturer for ingredient information, especially if you’re doing air monitoring or evaluating respiratory protection.

Third, CAS numbers let you look up additional toxicological data in NIOSH databases or the NTP Report on Carcinogens if you need more than what the SDS contains.

Section 4: First Aid Measures

The section that saves lives when used correctly. This covers what to do after skin contact, eye contact, inhalation, and ingestion. It also notes whether delayed effects exist, which matters because some chemical exposures don’t produce symptoms immediately.

The first aid information in this section should be posted or summarized near chemical use areas. Workers shouldn’t have to pull up a PDF to know whether to flush eyes for 15 minutes or 30 minutes after a splash.

Section 5: Firefighting Measures

Suitable and unsuitable extinguishing agents. Special hazards from combustion (some chemicals produce toxic decomposition products when they burn, which changes how fire response works). This section tells responders what kind of fire they’re dealing with and what not to use on it. Carbon dioxide works for some chemical fires and is completely wrong for others.

Section 6: Accidental Release Measures

Spill and leak response. Personal precautions (what PPE is needed before entering a spill area), environmental precautions (prevent drain entry, collect for disposal), and cleanup methods.

This is the section to reference when building your emergency response procedures for chemical releases. Walk the relevant work areas with the spill response section in hand. If the section calls for Level B PPE during spill response and your team doesn’t have it, that’s a gap to address before the spill happens.

Section 7: Handling and Storage

Compatible and incompatible materials, temperature requirements, ventilation requirements, and specific handling precautions. Some chemicals require grounding during transfer to prevent static discharge. Some require segregation from specific chemical classes. This section is where you find that.

Storage temperature limits also live here. A chemical that needs to stay below 80°F stored in an unventilated outdoor shed in July is a problem. Catch it here.

Section 8: Exposure Controls and Personal Protection

Safety professionals use this section more than any other. It contains:

The OSHA Permissible Exposure Limit (PEL). This is the legal ceiling for airborne exposure, set in 29 CFR 1910.1000 tables. It’s also the most outdated limit in the document. Most OSHA PELs were set in 1971 and haven’t been updated. They represent a floor, not a health-protective standard.

The NIOSH Recommended Exposure Limit (REL). Published by the National Institute for Occupational Safety and Health. These are more current than OSHA PELs for most substances and are based on more recent toxicological data. They’re not legally enforceable, but they’re health-based.

The ACGIH Threshold Limit Value (TLV). Published annually by the American Conference of Governmental Industrial Hygienists. These are updated more frequently than either OSHA or NIOSH values and are used by industrial hygienists as the working standard for exposure assessment. Use the TLV where the OSHA PEL is outdated. For most substances where the TLV and OSHA PEL differ, the TLV is the more protective number.

This section also specifies the engineering controls required (local exhaust ventilation, enclosure, dilution ventilation) and the PPE selection for each exposure route: respiratory, eye, skin, hand. Match the PPE selection in Section 8 to the tasks workers actually perform, not the worst-case scenario in the SDS.

Section 9: Physical and Chemical Properties

Appearance, odor, vapor pressure, flash point, boiling point, solubility, and other physical data. These properties feed directly into hazard assessment.

Flash point tells you at what temperature the liquid produces enough vapor to ignite. A low flash point means the chemical is flammable under normal working conditions.

Vapor pressure tells you how readily the chemical evaporates. High vapor pressure means more airborne concentration potential, which matters for inhalation exposure assessment and ventilation design.

Odor threshold relative to the exposure limit is critical. If a chemical has an odor threshold above its PEL, workers can’t smell it before they’re overexposed. That means odor is not a reliable warning. You can’t rely on workers to self-report exposure.

Sections 10 Through 16

Section 10 covers stability and reactivity, including conditions to avoid and incompatible materials (more specific than Section 7).

Section 11 is toxicological information, including routes of exposure, acute and chronic health effects, carcinogenicity classifications from NTP, IARC, and OSHA, and reproductive toxicity data. This section gets dense, but the carcinogen listings matter for OSHA’s cancer hazard provisions and for medical monitoring decisions.

Section 12 covers ecological information, including aquatic toxicity and persistence. Relevant for spill response and disposal planning, and increasingly relevant as state environmental agencies add requirements that layer on top of OSHA’s.

Section 13 is disposal considerations. How to dispose of the product and contaminated materials in compliance with federal, state, and local regulations. Note that this section frequently says to contact a licensed waste disposal firm rather than giving specific disposal instructions, which is acceptable because disposal requirements vary by jurisdiction.

Section 14 covers transport information by regulatory mode (DOT, IATA, IMDG). UN number, proper shipping name, hazard class, and packing group. If you’re shipping or receiving the chemical, this section drives labeling and placard requirements.

Section 15 is regulatory information. Chemical inventories (TSCA, DSL), state right-to-know lists, California Prop 65 listings, and other regulatory status. Useful for compliance tracking but not for day-to-day hazard management.

Section 16 contains other information, including the SDS revision date and a list of changes from the prior version. Check the revision date. An SDS from 2009 may not reflect current GHS classification or updated exposure limits.

Maintaining an SDS Library

OSHA requires that SDSs be accessible to employees in their work area during their shift. In practice, most employers use one of two approaches: binder-based systems organized by work area, or electronic SDS management software.

Electronic systems work well as long as access is genuinely immediate. A system that requires a password reset, a supervisor login, or a tablet that’s usually dead doesn’t meet the accessibility requirement. If you use electronic access, document your backup procedure for system outages.

Keeping SDSs current is an ongoing task. When a supplier reformulates a product, they’re required to send an updated SDS within three months. Build a process to receive updated SDSs and replace outdated ones. An outdated SDS is not just a compliance issue. It may have exposure limits or PPE requirements that no longer reflect current practice.

Start With Section 8

When you’re evaluating a new chemical for workplace use, Section 2 tells you the hazard classification. Section 8 tells you what to do about it. The exposure limits, engineering controls, and PPE requirements in Section 8 are the inputs to your hazard control decision. If you only have time to read one section before bringing a new chemical on site, read Section 8 first. The PPE selection, the ventilation requirements, and the comparison between the OSHA PEL and the more current ACGIH TLV are all there. Everything else in the document supports what Section 8 tells you to do.