PHMSA / 49 CFR Hazardous Materials Regulations (US)

US Domestic Rules for Transporting Lithium Batteries by Road, Rail, Air and Vessel

The Hazardous Materials Regulations (HMR), set out in 49 CFR Parts 171–180, are the US domestic counterpart to ADR/RID/ADN in Europe and the IMDG Code at sea — they govern how dangerous goods, including lithium cells and batteries, may be packaged, marked, documented and carried within the United States. The Pipeline and Hazardous Materials Safety Administration (PHMSA), an agency within the US Department of Transportation, writes and enforces the HMR. Where IATA DGR and IMDG Code apply once a shipment crosses a border or boards a plane or ship, the HMR is what governs a battery moving between two points inside the US by truck, van or rail car.

Published by: Pipeline and Hazardous Materials Safety Administration (PHMSA), US Department of Transportation

Core lithium battery section: 49 CFR § 173.185 (Lithium cells and batteries)

Materials of Trade exception: 49 CFR § 173.6

Related standard: UN 38.3 (transport testing — a prerequisite for HMR compliance, same as under IATA DGR, IMDG Code and ADR/RID/ADN)

Most recent amendment: HM-268C, part of the HM-268A–P rulemaking package published 4 August 2026, effective 3 September 2026

Scope

The HMR classes lithium metal and lithium-ion cells and batteries as Class 9 miscellaneous dangerous goods, whether shipped as standalone batteries, packed with equipment, or installed inside equipment. Section 173.185 sets out the baseline regime: cells and batteries must be of a type that has passed UN 38.3 testing, and above small-format thresholds they need UN-specification packaging, hazard labelling, and full shipping documentation. Two narrower carve-outs sit alongside this baseline — a “small battery” exception for cells and batteries below defined watt-hour and lithium-content thresholds, and a separate exception covering batteries moved for recycling or disposal. A third, and distinct, carve-out is the Materials of Trade (MOT) exception under §173.6, aimed at companies whose vehicles carry batteries and battery-powered tools as a normal part of doing business — landscaping, construction, tree service, catering and similar trades — rather than as a hazmat shipment in the ordinary sense.

Key Requirements

Design and testing: every lithium cell or battery moved under the HMR must be of a type that has passed the eight UN 38.3 tests (altitude, thermal cycling, vibration, shock, external short circuit, impact/crush, overcharge, forced discharge).

Packaging and marking: fully regulated shipments require UN-certified performance packaging, the lithium battery mark, and — above quantity thresholds — the Class 9 label and shipping papers identifying the UN number (UN 3480/3090 standalone, UN 3481/3091 packed with or contained in equipment).

Materials of Trade exception (§173.6): §171.8 defines a Material of Trade as hazardous material “carried by a private motor carrier in direct support of a principal business” — the classic case being a landscaper’s or contractor’s own tools and fuel riding along in a company van, rather than a shipment of goods being sold or delivered. Batteries falling under this definition can move under relaxed requirements provided they stay within defined per-unit and per-vehicle weight limits and are secured against short circuit and accidental activation.

Recent Amendment — HM-268C (effective 3 September 2026)

HM-268C is one part of a sixteen-rule package (HM-268A through HM-268P) that PHMSA published on 4 August 2026, most of which takes effect 3 September 2026. HM-268C specifically raises the Materials of Trade weight limits for lithium cells and batteries in §173.6:

Each cell or battery may weigh up to 30 kg (66 lb) individually.
The aggregate limit per motor vehicle rises to 500 kg (1,102 lb) — up from the previous 200 kg (440 lb) ceiling.
Batteries already installed in equipment (rather than carried loose) are excluded from that 500 kg aggregate cap entirely.
Eligible batteries must still have passed UN 38.3 testing and be packaged or secured to prevent short circuits, shifting, or accidental activation of the equipment they power.
Shipments carrying more than 30 kg of batteries under this exception still require the Class 9 label and UN identification number, and the vehicle operator must be told what hazardous materials are on board and which requirements apply.

PHMSA’s stated rationale is that the previous 200 kg ceiling was increasingly out of step with how much battery-powered equipment trade businesses — landscaping crews, mobile mechanics, event and catering companies — now carry as standard kit, given the shift toward cordless tools and portable power packs.

Related Standards

UN 38.3 — transport testing standard; a prerequisite for HMR-compliant shipment regardless of exception used
IATA DGR — governs the same batteries once they move by air
IMDG Code — governs sea freight
ADR/RID/ADN — the closest European analogue for road, rail and inland waterway

Disclaimer: this is not a definitive guide, just an indication and it is important that you always go back to the source for legislation.