What changed: HCS 2012 (Rev.3) → HCS 2024 (Rev.7)
On May 20, 2024, OSHA finalized the biggest update to the Hazard Communication Standard since 2012, amending 29 CFR 1910.1200 to align primarily GHS Revision 7. It is not a rewrite — labels, SDS, and the pictogram set you already know mostly carry over — but the classification criteria tightened in several physical-hazard classes, and OSHA added two hazard classes that did not exist before. The wizard above shows exactly how each of your current classes maps to the new ones.
The five changes that affect the most chemicals:
- Flammable gases split. Former Category 1 is divided into 1A and 1B; Category 2 remains. Pyrophoric and chemically unstable gases are sub-designations inside Category 1A — not separate hazard classes. 29 CFR 1910.1200 App. B.2
- New: Chemicals under pressure. A liquid or solid pressurized with a gas in a container — its own physical hazard class (Categories 1–3), distinct from aerosols. 29 CFR 1910.1200 App. B.3.2
- New: Desensitized explosives. Explosives phlegmatized to suppress their explosive properties — a new class (Categories 1–4). 29 CFR 1910.1200 App. B.17
- Aerosols Category 3. A new non-flammable aerosol category added within the existing Aerosols class (now Cat 1–3). 29 CFR 1910.1200 App. B.3
- Updated criteria for oxidizing liquids/solids, corrosive-to-metals, and several Appendix A health classes (acute toxicity, aspiration, skin/eye). 29 CFR 1910.1200 App. A & B
The two genuinely new physical hazard classes
Most of HCS 2024 is re-criteria, not re-class. But these two classes are brand new — if you ship aerosol-adjacent or energetic products, they are the highest-risk gaps in a transition audit:
| New hazard class | What it covers | CFR appendix |
|---|---|---|
| Chemicals under pressure | Liquids/solids pressurized with a gas in a container (non-aerosol). Categories 1–3. | 29 CFR 1910.1200 App. B.3.2 |
| Desensitized explosives | Explosives phlegmatized (wetted/diluted) to suppress explosivity. Categories 1–4. | 29 CFR 1910.1200 App. B.17 |
Source of truth: Desensitized Explosives (App. B.17), Chemicals Under Pressure (App. B.3.2), Aerosols (Categories 1–3, incl. new Cat 3 non-flammable) (App. B.3).
When you have to comply (the real deadlines)
The 2024 rule took effect July 19, 2024. A January 15, 2026 final rule (FR Doc. 2026-00653 (Jan 15) extended every compliance date by four months. These post-extension dates are what is now in force in the eCFR text of 29 CFR 1910.1200(j):
| Provision | Who | Deadline | CFR |
|---|---|---|---|
| Substances | Manufacturers, importers, distributors | May 19, 2026 | 29 CFR 1910.1200(j)(2)(i) |
| Substances | Employers (labels, program, training) | November 20, 2026 | 29 CFR 1910.1200(j)(2)(ii) |
| Mixtures | Manufacturers, importers, distributors | November 19, 2027 | 29 CFR 1910.1200(j)(3)(i) |
| Mixtures | Employers | May 19, 2028 | 29 CFR 1910.1200(j)(3)(ii) |
During the interim, you may comply with the 2012 HCS, the 2024 HCS, or both. State-Plan states (e.g. California, Michigan, Washington) adopt at least as effective a standard and may set their own dates.
Worked examples
Example 1 — a flammable-gas product. Your SDS lists a gas as Flammable gas, Category 1 under HCS 2012. Under Rev.7 you must decide between Category 1A and Category 1B against the new criteria, and check whether it is also pyrophoric or chemically unstable — both of which are now recorded as sub-designations of 1A, not as their own classes. The signal word and hazard statement may change; update Section 2 of the SDS and the label.
Example 2 — a pressurized cleaner that is not an aerosol. A solvent packaged as a liquid under nitrogen pressure was previously squeezed into "compressed gas" or left ambiguous. Under HCS 2024 it is a Chemical under pressure (App. B.3.2), a distinct class with its own categories, pictogram logic, and statements — a classification that simply did not exist before. This is the kind of product the wizard's questionnaire flags so it does not slip through your transition.
What to do next
- Inventory and map. Run every class through the wizard above and export the PDF for your file.
- Get updated SDS from your manufacturers/importers — they must reclassify by May 19, 2026 (substances).
- Reprint labels for any class whose category, signal word, or pictogram changed.
- Retrain employees as necessary on newly identified hazards and the new label elements before November 20, 2026 (substances) / May 19, 2028 (mixtures).
- Update your written HazCom program to reference HCS 2024.
Frequently asked questions
When does OSHA's HCS 2024 / GHS Rev 7 take effect?
The OSHA final rule aligning the Hazard Communication Standard primarily with GHS Revision 7 (89 FR 44144 (May 20, 2024)) took effect July 19, 2024. After a 4-month extension (FR Doc. 2026-00653 (Jan 15, 2026), +4 months), compliance for substances is due May 19, 2026 (manufacturers, importers, distributors) and November 20, 2026 (employers); for mixtures, November 19, 2027 (manufacturers, importers, distributors) and May 19, 2028 (employers).
What are the main GHS Rev 7 classification changes?
Key changes include: flammable gases subdivided into Categories 1A, 1B and 2 (with pyrophoric and chemically unstable gases as sub-designations inside Category 1A — not separate classes); two genuinely new physical hazard classes — desensitized explosives and chemicals under pressure; a new non-flammable Aerosols Category 3 within the existing Aerosols class; and updated oxidizing liquids/solids and corrosive-to-metals criteria. Health hazards (acute toxicity, aspiration, skin/eye) are also updated in Appendix A.
Do I need to reclassify my chemicals for GHS Rev 7?
Yes. Chemical manufacturers and importers must classify hazards according to the updated HCS (Appendix A and B). Employers must ensure labels and SDS reflect the new criteria. Use this wizard to see how older HCS 2012 / GHS Rev.3 classes map to the new categories.
Where can I find the official GHS Rev 7 criteria?
OSHA Appendix A (health hazards) and Appendix B (physical hazards) contain the mandatory classification criteria. The UNECE Purple Book (GHS Rev.7 and later) is the international source. OSHA's HazCom rulemaking page and the Federal Register final rule provide the full regulatory text.
Does HCS 2024 change labeling for small containers?
Yes. HCS 2024 added a "Small container labelling" paragraph — 29 CFR 1910.1200(f)(12) (added by the HCS 2024 final rule) — for manufacturer/importer/distributor shipped containers: a container of 100 mL or less may carry an abbreviated label when a pull-out label, fold-back label, or tag is not feasible, and a container of 3 mL or less may show the product identifier only where any label would interfere with normal use. The immediate outer package must still carry the full label, and it must state that the small containers are stored back in that package when not in use. These thresholds do not apply to in-house workplace/secondary containers.
Do employers have to retrain workers for HCS 2024?
Yes. Employers must update labels, the written program, and employee training for the new hazard classes and label elements by the employer deadlines — November 20, 2026 (substances) and May 19, 2028 (mixtures) — under 29 CFR 1910.1200(h) and (j)(2)(ii)/(j)(3)(ii). Train workers on any newly identified hazards, such as chemicals under pressure, desensitized explosives, and the flammable-gas Category 1A/1B split.
Sources & verification
- https://www.ecfr.gov/current/title-29/subtitle-B/chapter-XVII/part-1910/section-1910.1200
- https://www.federalregister.gov/documents/2026/01/15/2026-00653/hazard-communication-standard
- https://www.osha.gov/hazcom/rulemaking/extension
- OSHA Appendix A (health hazards) & Appendix B (physical hazards), 29 CFR 1910.1200.
Classifications and deadlines verified 2026-06-23. This wizard is a planning aid, not legal advice; confirm every classification against the OSHA final rule and the applicable appendix before relabeling.
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