DOT’s Pipeline and Hazardous Materials Safety Administration (PHMSA) issued a final rule on August 4, 2026 that significantly revises how aerosols are defined under the Hazardous Materials Regulations (HMR). The change—effective September 3, 2026—aligns U.S. rules with international standards and removes long‑standing limitations that created confusion and extra compliance burdens for shippers.
The Core Change: Aerosols Can Now Expel Gas Only
Under the previous definition in 49 CFR 171.8, an aerosol had to expel a liquid, paste, or powder. This meant that containers designed to release only gas were not considered aerosols under DOT rules—even though they were considered aerosols internationally.
PHMSA’s 2026 rule removes that requirement, allowing aerosols to consist solely of gases.
Old rule: Aerosol must expel a liquid/paste/powder New rule: Aerosol may expel gas only, consistent with UN Model Regulations and international transport standards.
Why PHMSA Made the Change
PHMSA explicitly states that the old definition caused:
- Lack of harmonization with international standards
- Increased compliance costs for global shippers
- Logistical inefficiencies for manufacturers and distributors
- Delays and trade barriers for cross‑border shipments
- Reduced competitiveness for U.S. companies
By updating the definition, PHMSA aims to reduce regulatory burdens without compromising safety.
Who Is Affected?
The rule applies to all offerors of aerosols, including:
- Manufacturers
- Warehouses and distribution centers
- Repackagers
- E‑commerce fulfillment centers
- Carriers handling consumer products containing compressed gases
If your facility ships any pressurized container with a self‑closing release device—even if it releases only gas—it may now fall under the aerosol provisions of the HMR.
Key Impacts on HazMat Shippers
1. More Products Now Classified as Aerosols
Items that previously fell under other hazard classes or packaging rules may now be reclassified as aerosols. Examples include:
- Gas‑only spray dusters
- Air fresheners that release gas
- Certain refrigerant or propellant cartridges
- Gas‑only technical sprays used in industrial settings
This may simplify classification for some products but requires careful review.
2. Packaging Requirements May Change
Aerosols must meet specific packaging and pressure‑testing requirements. Products newly classified as aerosols may need:
- DOT‑authorized aerosol containers
- Updated performance testing
- Revised closure/valve specifications
- New compatibility assessments
This could require packaging redesign or supplier changes for some shippers.
3. Marking & Labeling Updates
Aerosols have unique marking and labeling rules under the HMR. Newly covered products may require:
- Hazard class labels (e.g., Class 2 gases)
- UN identification numbers
- Proper shipping names
- Orientation arrows (for liquids)
Shippers must update artwork, label stock, and SOPs accordingly.
4. Shipping Paper Revisions
If a product’s hazard class or proper shipping name changes due to the new definition, shipping papers must be updated. Common changes may include:
- New UN numbers
- Revised packing groups
- Updated emergency response information
Carriers may reject shipments with outdated descriptions.
5. Training Requirements Expand
HazMat employees must be trained on:
- The new aerosol definition
- Revised classification procedures
- Updated packaging and labeling rules
- Any changes to facility SOPs
Training must be completed within 90 days for employees affected by regulatory changes.
6. Potential Cost Savings
PHMSA notes that harmonization will:
- Reduce confusion
- Lower compliance costs
- Improve efficiency for global shippers
- Reduce delays and rejected shipments
- Increase competitiveness of U.S. businesses
For many shippers, the rule may simplify operations—especially those already following international standards.
What HazMat Shippers Should Do Now
1. Conduct a Product Review
Identify any products that:
- Release only gas
- Were previously excluded from aerosol classification
- Use pressurized containers with self‑closing valves
These may now be aerosols under DOT rules.
2. Update Hazard Classifications
Reevaluate hazard classes, UN numbers, and packing groups for affected products.
3. Review Packaging Specifications
Confirm that containers meet DOT aerosol requirements.
4. Update SOPs, Labels, and Shipping Papers
Ensure all documentation reflects the new definition.
5. Retrain HazMat Employees
Training must cover the updated definition and any procedural changes.
6. Coordinate With Carriers and Suppliers
Ensure alignment across your supply chain to avoid shipment delays.
Conclusion
PHMSA’s 2026 aerosol definition update is a significant regulatory shift that brings U.S. rules in line with international standards. While the change may require reclassification and updates to packaging, labeling, and training, it ultimately reduces regulatory burdens and improves efficiency for HazMat shippers.