The Occupational Health and Safety Administration (OSHA) has updated its Hazard Communication Standard to improve chemical safety. OSHA, which operates under the U.S. Department of Labor, passed its final rule on updating chemical labeling and classifications for the first time since 2012. The rule will go into effect July 19, 2024, and aligns OSHA’s hazardous communications with the United Nations’ Globally Harmonized System of Classification and Labeling of Chemicals.

The final rule incorporates the following provisions and changes.

Hazard Classifications

New and updated hazard categories have been defined.

The Explosive Hazard Class has had two changes.

• Desensitized Explosives (which are diluted or wetted to form a solid mixture and suppress their explosive properties) has been added as a hazard, with four category classes based on burning rate.
• Explosive properties of a substance must be communicated on the Safety Data Sheet (SDS), even if the substance is not classified as an explosive.

The Flammable Gases Hazard Class has had multiple changes.

• Two subcategories have been added, pyrophoric (spontaneously igniting) and unstable gases. Either is now considered a Category 1A flammable gas. Pyrophoric gases are no longer a stand-alone class.
•  A new flammable gas subcategory has been added, Category 1B Flammable Gas, for gases with a lower flammability limit or burn velocity.

The Aerosol Hazard Class, formerly known as Flammable Aerosols, has had changes.

• Non-flammable aerosols have been added to this class, many of which had been listed under Gases Under Pressure, which resulted in over-warning.
• The term Chemicals Under Pressure has been introduced to avoid categorizing aerosols incorrectly.
• Aerosols in the above categories are no longer additionally classified as Gases Under Pressure, Flammable Liquids, or Flammable Solids.

Changes in other categories have been made.

• Classifications of solid chemicals in the Self-Heating Chemicals Hazard Class must be performed on the chemical in the form in which it occurs in the workplace.
• The Oxidizing Gases Hazard Class requires new testing to utilize test O.3.
• Category 3 of the Chemicals Which, in Contact with Water, Emit Flammable Gases Hazard Class has been updated to apply only to chemicals whose flammable gas evolution rate is greater than 1 liter/kg per hour when reacting with ambient temperature water.

Other changes were made to labeling and compliance procedures.

1. Clearer, simplified pictogram labels to reduce confusion between OSHA and Department of Transportation (DOT) hazardous materials labels
2. Relaxed requirements for small packaging labels, including simplified labels where standard ones are unfeasible
3. Changes to labeling requirements to minimize employee contact with hazardous materials in the process of applying warning labels
4. Extended compliance dates for manufacturers to meet compliance with the final rule

               a. The compliance date for chemical substances has been set to January 19, 2026.
               b. The compliance date for updating workplace hazcom programs, labeling, and training for chemical substances has been set to July 20, 2026.
               c. The compliance date for chemical mixtures has been set to July 19, 2027.
               d. The compliance date for updating workplace hazcom programs, labeling, and training for chemical mixtures has been set to January 19, 2028.