Reading a Safety Data Sheet: The Sections That Matter

Why this matters

A safety data sheet (SDS) runs sixteen sections and often ten or more pages, and nobody reads it standing in a customer's basement with a jug in one hand. They do not have to. On the spot, a tech needs answers to four questions, and four sections answer them: what can this do to me, how do I keep it from doing that, what do I wear, and what do I do if it happens anyway. A tech who knows where those four live gets the answer in under a minute on a phone. A tech who does not either skips it or scrolls past the one line that mattered.

The sixteen, and why most of them are not for you on the job

The Hazard Communication Standard (HazCom, 29 CFR 1910.1200, with the same requirements reaching construction work through 29 CFR 1926.59) fixes the order of the sixteen sections so every manufacturer's sheet reads the same way:

Sections 12 through 15 are required on the sheet for international alignment, but OSHA does not enforce their content, because those subjects belong to other agencies. That is useful to know when a Section 13 disposal line reads as vague: it was never written to be your disposal instruction.

The four sections, in the order the moment asks

Section 2, before you open it: what can this do to me? Look for three things. The signal word, which is "Danger" for the more severe hazards and "Warning" for the less severe; there is only ever one. The pictograms, the red-bordered diamonds: corrosion, flame, flame over circle (oxidizer), skull and crossbones, exclamation mark, health hazard (the silhouette), gas cylinder. And the hazard statements, the fixed sentences with H-codes such as H314 ("causes severe skin burns and eye damage"). The hazard statement tells you the route: skin, eyes, inhalation, ingestion. That route decides everything in Section 8.

Section 8, before you open it: what do I wear and what keeps the air clean? Two halves. The exposure limits, where the OSHA permissible exposure limit (PEL) is the legally enforceable airborne limit for an eight-hour shift and other limits listed (from ACGIH or NIOSH) are often lower and are guidance. And the controls: ventilation, eye and face protection, the glove material (a sheet that says "chemical-resistant gloves" without naming a material has left the question open; check the glove maker's chart), and whether a respirator is needed. A respirator named here is used only under a written respiratory protection program, 29 CFR 1910.134, with medical evaluation and fit testing. A tech who is not in the program does not do the task that needs one.

Section 7, while you work: how do I handle and store it? The handling half carries the instructions you are most likely to violate without noticing: do not mix with other products, add product to water and not water to product, do not use in confined spaces, keep containers closed. The storage half names conditions (temperature, keep dry) and points you to Section 10 for incompatibilities.

Section 4, when it goes wrong: what do I do right now? By route: eyes, skin, inhalation, ingestion. Read it once before you need it, because when you need it someone's eyes are burning and nobody is reading. The most common instruction for a corrosive in the eyes is to rinse with water for at least 15 minutes, holding the eyelids open, and then get medical attention. Ingestion instructions frequently say do not induce vomiting; follow the sheet, call Poison Control (1-800-222-1222 in the US) and take the SDS or the container with you to the emergency room. Section 1's emergency phone is the manufacturer's line and is also worth calling for advice on that specific product.

One more, for the planning stage

Section 10 is the mixing question. It lists incompatible materials and hazardous decomposition products, and it is the section that tells you whether the product in your hand will react with what is already in the drain, the pool or the mop bucket. It is not one of the four because it is rarely the question at the moment you open the container; it is the question before you decide to use it at all. Storage segregation by these families is owned by Pool and Cleaning Chemical Incompatibility in Storage.

What changed in the 2024 update

OSHA published revisions to HazCom in May 2024 to align with a later revision of the Globally Harmonized System (GHS). For a field tech the visible changes are modest: some hazard categories were reorganised (notably for aerosols and gases under pressure), small containers get relief from carrying a full label when there is no room, the date a container was released for shipment can appear on the label, and a manufacturer withholding an exact percentage as a trade secret must give a prescribed concentration range instead. The sixteen-section order did not change. Compliance dates for manufacturers and then for employers phase in from 2026 into 2028, with mixtures last. This is current as of 2026; check OSHA's Hazard Communication page for the dates that apply to your shop, and expect to see sheets in both the older and newer formats during the transition.

Worked example: a sheet read on a drain call

A tech arrives at a slow kitchen drain. The customer says they poured a bottle of crystal drain opener down it last night. The van carries a sulfuric acid drain opener. The tech pulls the sheet on the phone. An excerpt, condensed:

SECTION 2  HAZARD(S) IDENTIFICATION
Signal word: DANGER
Pictograms: corrosion
H314 Causes severe skin burns and eye damage
H290 May be corrosive to metals

SECTION 4  FIRST-AID MEASURES
Eyes: rinse with water at least 15 min, lids open.
      Get medical attention immediately.
Skin: remove contaminated clothing, rinse 15 min.
Ingestion: rinse mouth. Do NOT induce vomiting.

SECTION 7  HANDLING AND STORAGE
Always add product to water, never water to product.
Do not mix with other drain openers or chemicals.
Store away from bases, oxidizers, metals.

SECTION 8  EXPOSURE CONTROLS
Sulfuric acid mist: OSHA PEL 1 mg/m3 (8-hr TWA)
Eyes/face: chemical splash goggles and face shield
Hands: neoprene or butyl rubber gloves
Respiratory: not normally required with adequate
ventilation; if mist forms, use under a program.

SECTION 10  STABILITY AND REACTIVITY
Incompatible: strong bases (sodium hydroxide),
chlorine bleach, water in large amounts.

Reading it in the order the moment asks:

1. Section 2: Danger, corrosive, burns skin and eyes. The route is contact, with an inhalation route if it mists.
2. Section 7 says do not mix with other drain openers. Crystal drain openers are typically sodium hydroxide, a strong base, and Section 10 confirms bases are incompatible. Acid poured onto standing caustic in a trap reacts with violent heat and can erupt out of the drain toward the person bent over it.
3. The decision: the acid does not get used on this drain today. The tech switches to a mechanical cable, which Section 2 had nothing to say about because it is not a chemical decision, and tells the customer why.
4. Section 8 still applies, because the trap water now holds caustic and the cable will throw it. Splash goggles and a face shield, neoprene gloves, a towel over the drain opening while the cable runs.
5. Section 4 is pre-read, so that if the trap water splashes a forearm the tech already knows the answer: rinse 15 minutes, remove anything wet, get it looked at.

Note what the tech did not read: Sections 3, 5, 6, 9, 11 through 16. None of them answers a question that tech had at that sink. Note also what the right read prevented. A tech who scanned only Section 8, saw goggles and gloves, and poured anyway would have been wearing the right PPE for the wrong decision.

What would change the read. If the customer had poured nothing, the acid could be used as the label directs, and Sections 7 and 8 would govern. If the customer could not say what they poured, treat the drain as holding an unknown and do not add any chemical; that is the same answer as the caustic case, for a stronger reason. And if the van's copy of the sheet is a pre-2015 material safety data sheet in the old free-form layout, the four answers may be anywhere in it, which is a reason to replace it, not to skip it.

How to verify you can read one

Hand a tech a sheet for a product the shop carries and time them to the signal word, the glove material and the eye first-aid instruction. Under a minute for all three is the standard worth holding. If they have to scroll past Section 3 to find out what the product is, they are reading from the top, which is the habit to break.

References

• OSHA Hazard Communication Standard, 29 CFR 1910.1200, Appendix D (SDS sections) and the 2024 revision
• OSHA Respiratory Protection, 29 CFR 1910.134
• OSHA Table Z-1, 29 CFR 1910.1000, for permissible exposure limits
• See related: Reading a Safety Data Sheet for What It Actually Tells You; Keeping Safety Data Sheets Accessible in the Field; Pool and Cleaning Chemical Incompatibility in Storage