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SDS Authoring: How to Write a Safety Data Sheet

How to author a compliant safety data sheet — hazard classification first, the 16-section format, who is qualified to write it, and US (OSHA HCS) vs EU (REACH Annex II) rules.

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Writing a safety data sheet is often mistaken for a formatting exercise — dropping information into 16 boxes. In reality, authoring an SDS is a hazard-assessment task with a documentation step at the end. The format is the easy part; the demanding part is classifying the substance or mixture correctly, because every hazard statement, pictogram, precautionary phrase, and handling instruction on the sheet is downstream of that classification.

This article walks through how an SDS is authored: who is responsible for writing it, the classification step that everything depends on, how to populate the 16 sections, and the points where the United States (OSHA HCS) and the European Union (REACH Annex II) diverge. For the section-by-section content rules themselves, see Safety Data Sheet Format: 16 Sections Explained; this guide is about the process of producing one.

At a glance

An SDS is authored by — or on behalf of — the party that places the chemical on the market: in the US, the chemical manufacturer or importer; in the EU, the supplier. Authoring proceeds in three broad stages: classify the hazards against the applicable criteria, gather the data for all 16 sections, and write the sheet in the required format, language, and level of clarity. The frameworks differ in their detail — the US works from OSHA HCS Appendices A and B, the EU from CLP classification and REACH Annex II — but both put classification first and both demand internal consistency across the whole document. The legal responsibility for accuracy rests with the manufacturer or importer, whether the sheet is written in-house or outsourced.

Who must author an SDS

In the United States, the duty is explicit: chemical manufacturers and importers must obtain or develop an SDS for each hazardous chemical they produce or import, and the manufacturer or importer preparing the sheet is responsible for its content. Employers further down the chain are not required to author sheets — they must have one for each hazardous chemical they use, which normally means obtaining it from the supplier.

In the EU, the supplier of a substance or mixture must provide an SDS compiled in accordance with REACH Annex II whenever the product is classified hazardous (and, on request, for certain non-classified mixtures containing hazardous components). REACH adds a competence requirement that US law does not: the sheet must be prepared by a competent person, and suppliers must ensure those persons receive appropriate training, including refresher training. Downstream users and distributors who change a product’s use or re-supply it may also have to compile their own SDS.

Step 1: Classify the hazards

Classification is the foundation, and it is where most of the real work — and most of the errors — sit.

In the US, chemical manufacturers and importers must evaluate the chemicals they produce or import and classify them using the procedures in Appendix A (health hazards) and Appendix B (physical hazards) of 29 CFR 1910.1200. Two points matter for authoring: there is no requirement to test a chemical to classify it — the author must identify and consider the full range of available scientific literature and other evidence — and when classifying a mixture, the manufacturer or importer may rely on the current SDSs of the individual ingredients, unless they know (or reasonably should know) that an ingredient sheet misstates or omits required information.

In the EU, classification follows the CLP Regulation (EC No 1272/2008), which sets the hazard classes and categories, while REACH Annex II governs how the resulting information is laid out on the sheet. For mixtures, calculating an acute toxicity estimate (ATE) is a common step; an ATE calculator and a reference for hazard classes and statements help keep this stage accurate.

Only once classification is fixed can Section 2 (hazard identification), the label elements, and the precautionary advice throughout the sheet be written so that they agree with one another.

Step 2: Gather the data for all 16 sections

With classification settled, authoring becomes a data-collection task. Each section needs specific inputs: composition and ingredient identities (Section 3), first-aid and fire-fighting measures (Sections 4–5), physical and chemical properties (Section 9), toxicological and ecological data (Sections 11–12), disposal and transport information (Sections 13–14), and regulatory status (Section 15). Much of this comes from ingredient SDSs, supplier data, test reports, and authoritative databases.

A practical note on US scope: OSHA does not enforce the information requirements in Sections 12 through 15, because those subjects fall under other agencies (EPA, DOT). The sections must still appear in the sheet to be GHS-consistent, and almost every commercial US SDS completes them in full to meet international shipping and downstream-user expectations.

Step 3: Write to the format, language, and audience

The sheet must follow the fixed 16-section order. In the US the content rules are in Appendix D to 1910.1200; in the EU they are in Annex II. Beyond structure, the EU rules are explicit about quality: the information must be written clearly and concisely, in simple, precise language that avoids jargon, acronyms, and abbreviations, and tailored to the knowledge of the user audience.

Language is a hard requirement, not a courtesy. A US SDS must be in English (an employer may keep additional translations). An EU SDS must be provided in the official language(s) of every member state where the product is placed on the market, so a product sold across several EU countries needs a version per language.

EU specifics: exposure scenarios, the UFI, and revision history

Three EU details shape authoring beyond the basic 16 sections. First, extended SDS (eSDS): where a substance requires a Chemical Safety Report — generally substances registered above 10 tonnes per year per registrant — the supplier must attach exposure scenarios describing the safe conditions of use. Second, the UFI (Unique Formulation Identifier): hazardous mixtures placed on the EEA market require a UFI for poison-centre notification, and the current Annex II format (Regulation (EU) 2020/878) provides for it in subsection 1.1. Third, Section 16 revision history: ECHA guidance recommends clearly recording what changed in each revision — to an inspector, a vague or missing revision history signals a sheet that is not being actively maintained.

Keeping classifications current

Authoring is not a one-time act. Classifications change as criteria are revised, and a sheet has to be re-authored when they do. In the US, the HCS 2024 update aligns the standard with the seventh revised edition of the GHS, with compliance phasing in between May 2026 and May 2028 after the January 2026 deadline extension — see OSHA HCS 2024 Changes. In the EU, REACH Article 31(9) requires suppliers to update a sheet without delay when new hazard or risk-management information appears, when an authorisation is granted or refused, or when a substance is added to the Candidate List, and to re-supply recent recipients. Maintaining authored sheets over time is itself a discipline — covered in SDS Management.

Manual authoring vs software and services

A competent author can write an SDS by hand, working from ingredient data, classification criteria, and a template. For a single product in one market, that is entirely workable. The effort scales badly, though: every additional product multiplies the classification work, and every additional market adds a language version and a set of jurisdiction-specific rules.

SDS authoring software and outsourced authoring services exist to manage that scale. A capable tool applies the classification logic automatically, populates the 16 sections from a substance and ingredient database, formats the output for each target jurisdiction, and generates the required language versions — turning a multi-market authoring project from a manual rewrite per country into a single source that is re-rendered per market. The trade-off is cost and the need to keep the underlying data current; the legal responsibility for the result still belongs to the manufacturer or importer.

Common authoring mistakes

  • Skipping or rushing classification — building the sheet around an incomplete hazard assessment, so the rest of the document inherits the error.
  • Internal inconsistency — hazard statements, pictograms, and precautionary advice that do not match the stated classification.
  • Misusing “no data available” — using it as a catch-all instead of distinguishing “not relevant,” “not tested,” and “no information found.”
  • Stale revision — a sheet that predates current classification rules, with no revision history in Section 16.
  • Wrong language or format for the market — an English-only sheet supplied into the EU, or a sheet missing the UFI or exposure scenarios where they are required.

Key takeaways

  • Authoring an SDS is a hazard-classification task first and a formatting task second.
  • In the US, manufacturers and importers develop the sheet and classify using Appendices A and B; in the EU, a competent person compiles it under REACH Annex II using CLP classification.
  • There is no testing requirement to classify; authors weigh available literature and ingredient data, and mixtures may rely on ingredient SDSs.
  • The EU adds exposure scenarios (eSDS for CSR substances over 10 t/year), the UFI for hazardous mixtures, and per-member-state language requirements.
  • Sheets must be re-authored as classifications change (HCS 2024 phasing in through 2028; REACH Article 31(9) updates).

Sources

Frequently asked questions

Who is qualified to write a safety data sheet?

In the United States, OSHA does not require a licence or certification to author an SDS — chemical manufacturers and importers must develop one for each hazardous chemical they produce or import, and the practical demand is competent hazard classification rather than a formal credential. In the EU, REACH Annex II is stricter: the SDS must be prepared by a competent person, and suppliers must ensure those persons have received appropriate training, including refresher training. In both cases the real qualification is the ability to classify hazards correctly and document them consistently.

What is the first step in writing an SDS?

Hazard classification. Everything on the sheet flows from how the substance or mixture is classified, so authoring begins by evaluating the available data against the relevant criteria — Appendices A (health) and B (physical) of OSHA HCS in the US, or the CLP Regulation in the EU. There is no requirement to test a chemical to classify it; instead the author considers the full range of available scientific literature and ingredient data. Only once classification is settled can the hazard statements, pictograms, precautionary advice, and section content be filled in consistently.

Can I write an SDS myself, or should I use software or a service?

Either is possible. A competent in-house author can write an SDS manually, but the work is detailed — correct classification, 16 consistent sections, and (for the EU) the right language for each market. SDS authoring software and outsourced authoring services automate the classification logic, populate sections, format for each jurisdiction, and translate into the required languages, which is why larger manufacturers and exporters often use them. The legal responsibility for accuracy stays with the manufacturer or importer regardless of the tool.

What is the difference between a standard SDS and an extended SDS (eSDS)?

An extended SDS (eSDS) is a standard 16-section SDS with exposure scenarios attached as an annex. Under EU REACH, suppliers of substances that require a Chemical Safety Report — generally those registered above 10 tonnes per year per registrant — must provide the eSDS, and the exposure scenarios describe the conditions of use under which the substance can be handled safely. A standard SDS without exposure scenarios is used for substances and mixtures that do not trigger a Chemical Safety Report.

What language must a safety data sheet be written in?

In the United States, the chemical manufacturer or importer must ensure the SDS is in English (an employer may keep additional copies in other languages). In the EU, the SDS must be supplied in the official language(s) of each member state where the substance or mixture is placed on the market — so a product sold across several EU countries typically needs several language versions.