UN3536 Bulk Packaging Definition and Registration

July 29, 2026

Reference No. 25-0051

This letter is in response to your April 7, 2025 letter requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to hazmat registration for lithium batteries that comprise a battery energy storage system (BESS). You describe a scenario involving lithium batteries, installed in a Cargo Transport Unit (CTU). The bill of lading enclosed with your letter indicates the dimensions of the cargo transport unit of 19.11 feet long, 8.08 feet wide, and 9.07 feet tall (approximately 1,400 cubic feet), weighing approximately 77,000 pounds. You ask if this cargo transport unit would be considered a bulk packaging under the definition in § 171.8.

Yes. As defined in § 171.8, bulk packaging is defined as a packaging, other than a vessel or a barge, including a transport vehicle or freight container, in which hazardous materials are loaded with no intermediate form of containment. Because the batteries described in your letter are housed within a single container, and wired together as a single unit, rather than being separated into individual inner packages, the container is considered a bulk packaging. In addition, registration is required under § 107.601(a)(4) for any shipment of hazardous materials in a bulk packaging (see § 171.8 of this chapter) that has a capacity of at least 13.24 cubic meters (468 cubic feet) for solids.

I hope this information is helpful. Please contact us if we can be of further assistance.

Sincerely,

Alexander Wolcott
Acting Chief, Regulatory Review & Reinvention
Standards and Rulemaking Division