Interpretation Response #24-0082

Below is the interpretation response detail and a list of regulations sections applicable to this response.

Interpretation Response Details

Response Publish Date: 03/26/2025

Company Name: Office of Railroad, Pipeline and Hazardous Materials Investigations National Transportation Safety Board

Individual Name: Rachael Gunaratnam

Location State: DC Country: US

View the Interpretation Document

Response text:

March 26, 2025

Rachael Gunaratnam
Hazardous Materials Accident Investigator
Office of Railroad, Pipeline and Hazardous Materials Investigations
National Transportation Safety Board
490 L’Enfant Plaza, SW
Washington, DC 20594

Reference No. 24-0082

Dear Ms. Gunaratnam:

This letter responds to the September 11, 2024 letter that you submitted on behalf of the National Transportation Safety Board (NTSB). In that letter, NTSB asks the Office of Hazardous Materials Safety (OHMS) to clarify the requirements in the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) that apply to the bulk transport by vessel of lithium batteries that are installed in a battery energy storage system (BESS). NTSB's understanding is that the requirements in special provision (SP) 389 apply to "UN3536, Lithium batteries installed in cargo transport unit" because the BESS is a freight container that meets the definition of a cargo transport unit (CTU) under the HMR. Based on that understanding, NTSB presents a series of questions to OHMS about the applicability of certain requirements in the HMR to the BESS.

OHMS has paraphrased and answered your questions as follows:

Q1. What are the performance criteria or specifications for a freight container used as a CTU when transporting "UN3536, Lithium batteries installed in cargo transport unit"?

A1. A freight container meets the definition of a CTU under the HMR. As noted in your letter, a CTU is defined, in relevant part, as "a transport vehicle, a freight container, a portable tank or a multiple element gas container." 49 CFR § 176.2. A freight container is "a reusable container having a volume of 64 cubic feet or more, designed and constructed to permit being lifted with its contents intact and intended primarily for containment of packages (in unit form) during transportation." 49 CFR § 171.8. Additional performance criteria, as provided in SP 389 and assigned to the UN3536 entry in the Hazardous Materials Table, states that "the batteries must be securely attached to the interior structure of the cargo transport unit (e.g., by means of placement in racks, cabinets, etc.) in such a manner as to prevent short circuits, accidental operation, and significant movement relative to the cargo transport unit under the shocks, loadings, and vibrations normally incident to transport." 49 CFR § 172.102(c)(1)(389).

Q2. If the cabinet used for the BESS described in NSTB’s letter is a freight container that meets the definition of a CTU under the HMR, which standards or specifications apply when a CTU is used to transport “UN3536, Lithium batteries installed in cargo transport unit” by vessel or highway?

A2. The cabinet described in NTSB's letter that houses the BESS is a freight container that meets the definition of a CTU as defined in the HMR. See 49 CFR § 176.2. There are requirements in the HMR for CTUs such as the one in the BESS described. See answer A1 for the relevant performance criteria in SP 389.

Q3. Is a "high sea state" with significant speed winds and wave heights considered normal conditions for the transportation of hazardous materials by vessel?

A3. The HMR do not specifically define conditions normally incident to transportation; however, a "high sea state" refers to rough and potentially dangerous ocean conditions with large waves, typically caused by strong winds or storms. While it is not unreasonable for a vessel to expect to encounter such rough seas during an ocean crossing, depending on the severity of the storm, such conditions may be considered abnormal.

Q4. Does the fact that the air conditioning system for a BESS is not energized during transportation imply that such a system is not "necessary for the safe and proper operation of the cargo transport unit" under SP 389 and the HMR?

A4. No. The mere fact that the air conditioning system for a BESS is not operating in transportation does not mean that such a system is not necessary for the safe and proper operation of the CTU in accordance with SP 389 and the HMR. An air conditioning system could be necessary for the safe and proper operation of the CTU if the BESS is in operation and actively providing power external to the CTU. The fact that the system is not operational during transportation would not affect the compliance obligations imposed under SP 389 and the HMR. If, on the other hand, an air conditioning system is only used for purposes other than the safe and proper operation of the CTU, the standard prescribed in SP 389 and the HMR would not be met. In this case, the air conditioning system must not be transported within the CTU.

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

Sincerely,

T. Glenn Foster
Chief, Regulatory Review and Reinvention Branch
Standards and Rulemaking Division

176.2, 171.8, 172.102(c)(1)(389)

Regulation Sections