The Occupational Safety and Health Administration’s updated Hazard Communication Standard is no longer a distant regulatory development. The first major compliance deadline has passed, and additional deadlines affecting workplace labels, safety data sheets, hazard communication programs, and employee training are approaching.
OSHA published the updated Hazard Communication Standard, commonly called HCS 2024, on May 20, 2024. The rule became effective on July 19, 2024, and primarily aligns the U.S. standard with Revision 7 of the United Nations’ Globally Harmonized System of Classification and Labelling of Chemicals.
Chemical manufacturers, importers, distributors, and employers should now determine which parts of the updated standard apply to their products and operations—and whether existing hazard classifications, labels, safety data sheets, and workplace procedures remain compliant.
Why Did OSHA Update the Hazard Communication Standard?
OSHA’s Hazard Communication Standard is intended to ensure that workplace chemical hazards are properly classified and clearly communicated to employers and employees.
Chemical manufacturers and importers are responsible for classifying the hazards of the chemicals they produce or import. Employers must communicate those hazards through workplace labels, safety data sheets, written hazard communication programs, and employee information and training. Distributors are responsible for transmitting required hazard information to downstream users.
The 2024 update does not replace the fundamental structure of the Hazard Communication Standard. Instead, it revises and clarifies several classification, labeling, and documentation requirements.
According to OSHA, the changes are intended to:
- Improve the accuracy and usefulness of chemical hazard information
- Incorporate new and revised hazard classes and categories
- Clarify obligations that caused uncertainty under the 2012 standard
- Improve precautionary statements
- Better coordinate requirements with other U.S. agencies
- Increase alignment with international trading partners, including Canada
For regulated companies, the practical effect is that some products may require reclassification, revised label elements, updated SDS content, or changes to workplace hazard communication procedures.
OSHA HazCom 2024 Compliance Deadlines
OSHA adopted a phased compliance schedule that separates substances from mixtures and gives employers additional time to update workplace programs after manufacturers and importers revise product information.
OSHA extended the original deadlines by four months in January 2026. The current schedule is as follows.
May 19, 2026: Labels and SDSs for Substances
Chemical manufacturers, importers, and distributors evaluating substances were required to comply with the modified HCS provisions and update applicable labels and safety data sheets by May 19, 2026.
Because this deadline has passed, organizations that manufacture or import chemical substances should confirm that affected products have been evaluated under HCS 2024.
November 20, 2026: Employer Updates for Substances
Employers have until November 20, 2026 to update workplace labels, written hazard communication programs, and employee training as necessary for substances.
This does not necessarily mean that every employee must receive a completely new training program. Employers should determine whether updated classifications, label elements, SDS information, or workplace hazards introduce information employees have not previously been trained to understand.
November 19, 2027: Labels and SDSs for Mixtures
Chemical manufacturers, importers, and distributors must update labels and safety data sheets for mixtures by November 19, 2027.
Mixture evaluations may depend on updated information received from individual ingredient suppliers. Companies should avoid waiting until the final months before the deadline to begin gathering revised SDSs and reviewing formulation data.
May 19, 2028: Employer Updates for Mixtures
Employers must update workplace labels, hazard communication programs, and training as necessary for mixtures by May 19, 2028.
During the applicable transition periods, regulated organizations may comply with the previous version of the Hazard Communication Standard, HCS 2024, or both. The transition period ends for each requirement when its corresponding compliance deadline arrives.
Major Changes Under HCS 2024
The significance of HCS 2024 extends beyond updating dates or replacing older documents. The rule affects how certain hazards are identified and how that information is communicated throughout the supply chain.
1. Hazard Classifications Must Consider Changes in Physical Form
HCS 2024 clarifies that chemical manufacturers and importers must consider hazards associated with a change in a chemical’s physical form.
A product that is relatively stable in the form in which it is sold may create a different hazard when it is cut, ground, heated, sprayed, pulverized, or otherwise altered during a known or reasonably anticipated use.
For example, a solid material may generate respirable particles or combustible dust when processed. A liquid may form a mist when sprayed. These potential hazards should be considered when the uses or applications are known or reasonably anticipated.
This change makes it important for manufacturers and importers to look beyond the packaged product and assess how customers are reasonably expected to handle or process it.
2. Chemical Reaction Products May Need to Be Evaluated
The updated classification language also addresses chemical reaction products associated with known or reasonably anticipated uses or applications.
OSHA does not require a manufacturer to predict every conceivable downstream use. However, classifiers must account for uses they know about or can reasonably anticipate. This may include uses advertised on product packaging, described in technical literature, identified through customer communications, or commonly associated with the product’s intended market.
This requirement may be especially relevant for:
- Industrial chemicals used in manufacturing processes
- Cleaning and sanitation products
- Coatings, adhesives, and sealants
- Products that release gases when combined with other materials
- Chemicals that decompose or react when heated
- Raw materials used in predictable downstream applications
A review of product stewardship information, technical data sheets, customer applications, and known processing conditions may be necessary to support an appropriate classification.
3. Revised Physical Hazard Categories
HCS 2024 modifies criteria affecting several physical hazard classes. OSHA specifically identified changes involving flammable gases, desensitized explosives, aerosols, and chemicals under pressure.
Among the changes:
- The flammable-gas category structure has been expanded.
- Desensitized explosives have been added as a physical hazard class.
- Aerosol classifications have been updated, including an additional hazard category.
- Requirements addressing chemicals under pressure have been incorporated into the standard.
- Label elements and precautionary statements have been updated for new or revised hazards.
Manufacturers and importers should determine whether any products previously classified under broader categories now fall within a newly created or revised category.
4. Updated Health-Hazard Criteria
OSHA revised portions of the health-hazard criteria to improve alignment with newer GHS provisions.
Updates include changes involving skin corrosion and irritation, serious eye damage and eye irritation, and the use of certain non-animal testing methods when evaluating skin effects.
A company should not assume that a previous classification remains correct merely because the formulation has not changed. Changes to classification criteria can affect a product even when its ingredients and concentrations remain the same.
5. New Provisions for Small and Very Small Containers
HCS 2024 includes specific labeling provisions for containers of 100 milliliters or less and very small containers of 3 milliliters or less.
These provisions are designed to address situations in which the full required label information cannot be displayed legibly on the immediate container. The update is also intended to improve alignment with Canada’s Workplace Hazardous Materials Information System.
Companies using abbreviated labeling options should carefully review the conditions attached to those options. The outer packaging, immediate container, product identifier, and instructions for keeping the container with its outer package may all require consideration.
Small-container relief should not be treated as a general exemption from hazard communication.
6. Label Updates for Products Released for Shipment
The rule adds flexibility for certain packages that have already been released for shipment.
Under the previous framework, questions arose about whether a company had to retrieve and relabel products that had already been packaged and staged for distribution when new hazard information became available.
HCS 2024 defines “released for shipment” and clarifies the circumstances under which manufacturers, importers, or distributors may avoid relabeling packages that have already reached that stage. The definition was developed to improve alignment with terminology used by the Environmental Protection Agency.
Companies relying on this provision should maintain procedures that clearly document when a product is considered released for shipment.
7. Changes to Safety Data Sheet Content
HCS 2024 includes revisions affecting multiple portions of the 16-section SDS format.
OSHA’s guidance identifies changes to SDS Sections 2, 3, 9, and 11, while its enforcement directive also notes revisions affecting Sections 1, 8, 10, and 14.
Depending on the product, revisions may involve:
- Updated hazard classifications
- New or revised hazard statements
- Ingredient concentration information
- Physical and chemical properties
- Stability and reactivity information
- Toxicological information
- Exposure-control information
- Transportation-related information
An SDS update should be based on a complete technical evaluation. Simply changing a revision date or inserting new regulatory language may not be sufficient.
8. Prescribed Concentration Ranges for Trade Secrets
HCS 2024 changes how certain ingredient concentrations may be reported when a company claims the exact concentration as a trade secret.
When an exact percentage or percentage range is withheld as a trade secret, the SDS must use one of OSHA’s prescribed concentration ranges. These ranges are intended to improve consistency and align more closely with Canada’s WHMIS requirements.
Companies should review SDS Section 3 disclosures to determine whether current trade-secret ranges conform to the updated requirements.
This review should involve both regulatory and technical personnel. The selected range must protect legitimate confidential business information while still communicating sufficient information to support hazard evaluation and emergency response.
What Employers Should Do Before November 20, 2026
The November 2026 deadline is particularly important for employers that use hazardous chemical substances but do not manufacture or import them.
A practical workplace review should include the following steps.
Review the Chemical Inventory
Compare the workplace chemical inventory with the SDS library. Confirm that product identifiers match and that obsolete products or duplicate records have been addressed.
Collect Updated Safety Data Sheets
Contact suppliers when updated SDSs have not been received for substances that may be affected by HCS 2024.
Employers are generally permitted to rely on classifications performed by manufacturers or importers. However, they still need current hazard information to maintain an effective workplace program.
Review Workplace Labels
Determine whether secondary-container labels, process-container labels, tank markings, and other workplace warnings remain consistent with the updated hazard information.
Update the Written Hazard Communication Program
The written program should accurately describe how the employer manages:
- Workplace labeling
- SDS access
- Employee information and training
- Non-routine chemical tasks
- Unlabeled pipes
- Multi-employer workplace communication
- Chemical inventory management
OSHA requires employers to develop, implement, and maintain a written hazard communication program at each workplace where the standard applies.
Determine Whether Additional Training Is Necessary
Training should be updated when employees may encounter a new chemical hazard they have not previously been trained to recognize.
Employers should consider whether revised pictograms, hazard statements, classifications, handling precautions, or emergency measures require additional instruction.
Document the Review
Maintain records showing which SDSs, labels, procedures, and training materials were reviewed, what changes were made, and when those changes were implemented.
Documentation can help demonstrate that compliance decisions were deliberate and based on the information available at the time.
What Manufacturers and Importers Should Do Now
For companies subject to the May 19, 2026 substance deadline, the focus should be on confirming that required work has been completed and identifying any gaps.
A post-deadline compliance review should address:
- Whether all applicable substances were identified
- Whether revised classification criteria were applied
- Whether known and reasonably anticipated uses were evaluated
- Whether physical-form changes and reaction products were considered
- Whether SDSs were updated
- Whether shipped-container labels were updated
- Whether downstream customers received revised information
- Whether trade-secret concentration ranges are compliant
- Whether small-container labels meet the new provisions
- Whether internal records support each classification decision
At the same time, companies that manufacture mixtures should begin preparing for the November 19, 2027 deadline.
Mixture updates may require substantial coordination across regulatory, toxicology, product stewardship, procurement, quality, and information-technology teams. Updated ingredient data may arrive at different times, and each change can affect classification calculations, SDS content, label artwork, packaging inventories, and customer communications.
Avoid Treating HCS 2024 as a Document-Formatting Project
One of the most significant mistakes a company can make is viewing HCS 2024 as a simple template update.
Compliance begins with scientific and regulatory evaluation. Label and SDS revisions are the results of that evaluation—not substitutes for it.
A defensible process may require:
- Reviewing the complete formulation
- Evaluating available toxicology information
- Assessing physical and chemical properties
- Applying mixture classification rules
- Evaluating foreseeable processing conditions
- Identifying reaction or decomposition hazards
- Reviewing confidential ingredient disclosures
- Reconciling OSHA requirements with other jurisdictions
- Documenting the scientific basis for classification decisions
Automated SDS software can support document production, but software alone cannot resolve incomplete data, interpret ambiguous studies, assess unusual downstream uses, or determine the most scientifically supportable classification.
How Experien Health Sciences Can Help
Experien Health Sciences helps companies evaluate chemical hazards and translate complex scientific information into clear, defensible regulatory documentation.
Support may include:
- HCS 2024 gap assessments
- Chemical hazard classification
- Toxicology data review
- Safety data sheet authoring and revision
- Label-content review
- Mixture classification
- Trade-secret ingredient disclosure review
- Product stewardship support
- Regulatory toxicology consultation
- Cross-jurisdictional SDS and labeling strategy
Whether your organization is addressing a missed substance deadline, preparing workplace updates for November 2026, or beginning the more extensive mixture review process, early action can reduce rushed decisions and prevent inconsistent hazard communication across products and facilities.
Prepare for the Next HazCom Deadline Now
HCS 2024 affects more than the appearance of labels and safety data sheets. It changes how certain hazards are classified, how foreseeable uses are considered, how small containers may be labeled, and how confidential ingredient concentrations must be presented.
The substance-related deadlines make this an immediate compliance issue, while the mixture deadlines create a longer—but still limited—implementation window.
A structured review now can help your company identify missing data, prioritize affected products, update workplace procedures, and prepare accurate hazard communication materials before the next deadline.
Need assistance evaluating your HCS 2024 obligations? Contact Experien Health Sciences to discuss hazard classification, toxicology review, SDS authoring, labeling, and regulatory compliance support.
This article is provided for general informational purposes and does not constitute legal advice. Regulatory requirements should be evaluated in relation to the specific products, operations, jurisdictions, and facts involved.
