How to Read a Safety Data Sheet (SDS)

Every hazardous chemical sold for professional use comes with a Safety Data Sheet (SDS), sometimes still called a Material Safety Data Sheet (MSDS). It’s the most complete source of safety information about that substance: what it can do to you, how to handle it, what to do in an emergency and how to get rid of it. Under the Globally Harmonized System (GHS), used in most countries, every SDS follows the same 16-section format, so once you know how to read one, you can read them all.

This guide explains what’s in each section, which sections matter most for different situations, and then walks through an example.

Why the SDS matters

• The label on a bottle gives a summary. The SDS gives the detail.
• A risk assessment should be based on the SDS.
• In an emergency, the SDS tells first aiders and firefighters what they’re dealing with.
• The same chemical can have different hazards at different concentrations, and the SDS for each product reflects that.

Always use the SDS for the exact product you have (supplier, grade and concentration), and make sure it’s reasonably current.

The 16 sections

Section 1: Identification

The product name, the supplier’s contact details, an emergency phone number, and recommended uses (and uses advised against).

Section 2: Hazard(s) identification

The most important section for a quick check. It gives:

• the hazard classification (e.g. “Skin corrosion, category 1B”)
• the signal word: Danger (more severe) or Warning (less severe)
• the GHS pictograms: see hazard symbols (GHS)
• hazard statements (H statements): coded descriptions of the hazard, e.g. H314 “Causes severe skin burns and eye damage”, H225 “Highly flammable liquid and vapour”
• precautionary statements (P statements): coded instructions, e.g. P280 “Wear protective gloves/protective clothing/eye protection/face protection”, P305+P351+P338 (the eye-contact first-aid instruction: rinse cautiously with water for several minutes, remove contact lenses if easy to do, continue rinsing)

The codes are standard worldwide, which helps when reading sheets in other languages.

Section 3: Composition / information on ingredients

The chemical identity, CAS number (a unique registry number for each substance) and concentrations of hazardous components. For mixtures, each hazardous ingredient is listed.

Section 4: First-aid measures

What to do after inhalation, skin contact, eye contact or swallowing, plus the most important symptoms and whether they may be delayed. Read this before you start work, not after an accident.

Section 5: Firefighting measures

Suitable and unsuitable extinguishing media. For example, water must not be used on some reactive metals, and a water jet can spread burning solvents. It also lists hazardous combustion products (such as toxic gases released when the substance burns).

Section 6: Accidental release measures

How to deal with spills: personal precautions, how to contain the spill, what absorbent or neutraliser to use, and how to prevent it reaching drains.

Section 7: Handling and storage

Safe handling practices (such as “use only in a well-ventilated area” or “keep away from ignition sources”) and storage conditions, including incompatible materials. See chemical storage and incompatible chemicals.

Section 8: Exposure controls / personal protection

• Occupational exposure limits: the maximum airborne concentration a worker may be exposed to, often averaged over 8 hours, and sometimes a short-term (15-minute) limit.
• Engineering controls: e.g. use a fume cupboard or local exhaust ventilation.
• Personal protective equipment (PPE): eye protection type, glove material (and sometimes breakthrough time), protective clothing and respiratory protection.

The glove information here is critical. As the lab accident case studies show, the wrong glove material can give almost no protection.

Section 9: Physical and chemical properties

Appearance, odour, pH, melting and boiling points, flash point (the lowest temperature at which the vapour can ignite), explosive limits, vapour pressure, density and solubility. These explain why a substance behaves as it does. A low flash point, for example, means a liquid gives off enough vapour to ignite at room temperature.

Section 10: Stability and reactivity

Conditions to avoid (heat, light, moisture), incompatible materials and hazardous decomposition products.

Section 11: Toxicological information

How the substance enters the body (routes of exposure), symptoms, acute toxicity data (such as LD₅₀ values from animal studies), and long-term effects such as carcinogenicity or reproductive toxicity.

Section 12: Ecological information

Toxicity to aquatic life, persistence, bioaccumulation and mobility in soil.

Section 13: Disposal considerations

How to dispose of the substance and its container safely. See disposing of chemical waste responsibly.

Section 14: Transport information

UN number, transport hazard class and packing group, used by carriers.

Section 15: Regulatory information

Laws and regulations that apply in particular countries.

Section 16: Other information

Date of preparation or last revision, abbreviations, and sources.

Which sections to read, when

Situation	Sections to read first
Planning an experiment	2, 7, 8, 9, 10, 13
Choosing gloves and eye protection	8
Someone has been exposed	4 (then 11)
A spill	6 (and 8 for PPE)
A fire	5
Storing a new chemical	7, 10
Disposing of waste	13

Worked example: concentrated hydrochloric acid (about 37%)

Here is how a student might summarise a typical SDS for concentrated hydrochloric acid. (Always use the sheet for the actual product in your lab; details vary by supplier and concentration.)

• Section 2: Signal word Danger. Pictograms: corrosion, and exclamation mark. Typical H statements include H290 (may be corrosive to metals), H314 (causes severe skin burns and eye damage) and H335 (may cause respiratory irritation).
• Section 4: Eyes: rinse immediately with plenty of water for at least 15 minutes and get medical help. Skin: remove contaminated clothing, rinse with water.
• Section 6: Contain the spill, neutralise with a suitable neutraliser (such as sodium hydrogencarbonate) and absorb; keep out of drains. See acid spills and safety.
• Section 7: Store in a cool, ventilated place, away from bases and metals. Keep containers closed.
• Section 8: Use in a fume cupboard; wear chemical splash goggles, suitable acid-resistant gloves and a lab coat.
• Section 9: Colourless to slightly yellow liquid with a pungent odour; gives off hydrogen chloride fumes; pH below 1.
• Section 10: Reacts with metals to give flammable hydrogen gas; reacts with oxidising agents such as bleach to release chlorine.

Resulting risk assessment controls: dispense concentrated acid only in the fume cupboard; wear goggles, gloves and lab coat; have neutraliser and eyewash available; dilute by adding acid to water, never water to acid. See strong acids.

Common mistakes

• Relying only on the bottle label.
• Using the SDS for the concentrated substance when working with a dilute solution (or vice versa). Hazards can differ greatly.
• Skipping section 8’s glove information and grabbing whatever gloves are nearest.
• Reading section 4 only after an accident has happened.
• Using an out-of-date sheet.

Key takeaways

• An SDS has 16 standard sections under the GHS, in the same order worldwide.
• Section 2 (hazards, pictograms, H and P statements) gives a quick overview.
• Sections 4, 5 and 6 are for emergencies; read them before you start.
• Section 8 specifies exposure limits, engineering controls and the correct PPE, including glove material.
• Base every risk assessment on the SDS for the exact product and concentration you’re using.