HazCom 2024: What Actually Changed, and the Deadlines That Just Moved

If you author safety data sheets or classify chemicals for a living, HazCom 2024 is the most consequential change to U.S. hazard communication in over a decade. OSHA published the final rule on May 20, 2024, and it took effect July 19, 2024. It pulls the Hazard Communication Standard (29 CFR 1910.1200) into alignment with the 7th revised edition of the UN's Globally Harmonized System (GHS Rev 7), with a handful of provisions pulled forward from Rev 8. The previous HCS was aligned to GHS Rev 3, so this is roughly four revisions of drift being corrected at once.

Then, in January 2026, OSHA moved the goalposts. Below is what changed in the standard itself, followed by the compliance timeline as it stands now.

The deadline extension you need to know about

On January 15, 2026, OSHA published a final rule extending every HazCom 2024 compliance deadline by four months. The agency's stated reason was that it had not finished publishing the guidance materials the regulated community needs, and the first deadline — substance manufacturers, originally January 19, 2026 — was days away.

During the extended window, you may comply with the 2012 standard, the 2024 standard, or both. Here is the current timeline:

The substance deadline is the one already in your rearview or fast approaching, depending on when you read this. If you make mixtures, you have more runway — but the reclassification work underneath a mixture SDS is exactly the part that takes longest, so the extra months are not slack.

What actually changed in the standard

The headline is "alignment with GHS Rev 7," but the practical changes that touch classification and SDS authoring are specific:

New and revised hazard classes. Aerosols were expanded to cover non-flammable aerosols under a new Category 3. A new class for chemicals under pressure was added, adopted from GHS Rev 8, covering liquids or solids pressurized with a gas. Desensitized explosives became their own hazard class, recognizing that a properly stabilized product handles very differently from a raw explosive. And pyrophoric gases and chemically unstable gases are now classified as Category 1A flammable gases rather than being shoehorned in through the definition of "hazardous chemical."

Classification now considers all foreseeable use. Manufacturers must evaluate hazards across the ways a chemical can reasonably be used and the conditions it can encounter downstream — including reaction hazards that could arise in the workplace — not just the single intended use. This is a meaningful expansion of the classifier's burden.

Concentration ranges and confidential business information. The rule updates how concentration ranges can be used on the SDS, tied to the CBI provisions. You can still protect a trade-secret concentration, but the range you disclose has to be narrow enough that it doesn't obscure the hazard, and you have to flag that the exact value is withheld. (More on the mechanics of this in a separate post — it's a place SDS authors routinely get tripped up.)

Section 9 gets more prescriptive. Physical and chemical property requirements in Section 9 were tightened, with more specific expectations about what gets reported and how.

Labeling cleanups. The rule codifies long-standing OSHA interpretations on labeling very small containers, clarifies labeling for bulk shipments, and adds a "released for shipment" provision that addresses product already in the distribution chain when new hazard information emerges.

One housekeeping note: OSHA issued correction notices in early 2025 fixing typos and errors in the regulatory text and appendices of the original rule. If you're working from a copy of the May 2024 Federal Register text, make sure you're reading the corrected version.

What this means for your SDS library

Every classified substance and mixture you ship needs to be re-evaluated against the Rev 7 criteria, and any SDS and label that changes as a result needs to be reissued. For a formulator with even a modest catalog, that is not a one-afternoon project — it's a structured reclassification pass across your whole library, with documentation to show your work if an inspector asks.

The reclassification logic itself hasn't become more ambiguous; it's become more specific. New cut-offs, new classes, and the "all foreseeable uses" expansion mean more rules to apply consistently across more products. That is precisely the kind of work where a deterministic, auditable classification engine earns its keep: the same inputs produce the same verdict every time, and you can trace exactly which criterion drove each classification.

If you want to pressure-test where your catalog stands against HazCom 2024, GHSLogic runs classifications against the current U.S. criteria and shows the rule path behind every result — so when you reissue an SDS, you can document why it says what it says.

This post is general regulatory information, not legal or compliance advice. Confirm current requirements against the published HCS (29 CFR 1910.1200) and OSHA's HazCom rulemaking page before making compliance decisions.