PHMSA Proposes Hazmat Rule Updates to Match UN, IMO, ICAO Standards
PHMSA proposed changes to the Hazardous Materials Regulations (49 CFR parts 171-180) to keep pace with the 2027-28 ICAO Technical Instructions, IMDG Code Amendment 43-26, 2024 Transport Canada updates and the 24th revised UN Model Regulations. The agency said the biennial international updates take effect or publish by January 1, 2027.
The proposal would add new entries to the Hazardous Materials Table, including separate UN numbers for lithium metal and sodium ion batteries installed in cargo transport units, splitting them from the existing lithium-ion-only entry. PHMSA cited a 2024 truck fire near Baker, California, where responders could not quickly tell which battery chemistry was involved, as a reason for the split.
Other changes include new packing group entries for butyl acrylates, vanadium pentoxide and chlorophenols, updated subsidiary hazard labels for ethylene oxide and related chemicals, and a clarified definition of "large packaging" based on internal rather than external volume. PHMSA also proposes updates to roughly a dozen incorporated ISO cylinder and tank standards.
PHMSA declined to adopt several other international changes, including revised cylinder definitions and a UN indicative list of infectious substances, saying current HMR provisions already cover the ground.
What's next
- Comments are due 60 days after Federal Register publication, scheduled for 2026-10-27; the exact deadline date was not yet inserted in the pre-publication text.
- PHMSA says it will reconcile overlapping provisions with the separate pending HM-215R rulemaking (91 FR 5996) once that rule is finalized.
All sources
- Proposed Rule (public inspection): Hazardous Materials: Harmonization with International Standards — Federal Register public inspection (Pipeline and Hazardous Materials Safety Administration), 2026-10-27
