The US Department of Transportation (DOT) on Feb. 27 issued an interim final rule that prohibits passenger airlines from carrying rechargeable lithium-ion (Li-ion) cells or batteries as cargo, noting their potential of causing uncontrollable fire in cargo holds.

The interim rule, a regulation issued without advance public notice as a proposed rule, also requires that Li-ion batteries and cells be shipped at no more than a 30% state of charge aboard cargo-only aircraft.

The rule does not restrict passengers or crew from bringing on board personal electronic devices containing Li-ion batteries, or restrict cargo airlines from transporting batteries or cells exceeding 30% of charge when packed or contained in devices.

Issued by the department’s Pipeline and Hazardous Materials Safety Administration (PHMSA), the interim rule responds to direction by Congress in the FAA Reauthorization Act of 2018 to conform US regulations with international standards promulgated by ICAO.

Many US passenger airlines already prohibit the carriage of Li-ion batteries in their cargo holds in line with standards adopted by ICAO, which became effective in April 2016.

In the rule text, the PHMSA references research conducted by the FAA’s William J. Hughes Technical Center, the NTSB and other sources into the fire hazard presented by the power source used for innumerable electronic devices.

“The FAA Technical Center’s research found that lithium batteries subject to certain conditions could result in adverse events, such as smoke and fire, that could impair the safe operation of the aircraft,” the rule states. “Specifically, they found that in a lithium battery fire, flammable gases could collect, ignite and ultimately exceed the capabilities of an aircraft’s fire suppression system.”

The potential for a catastrophic loss of an aircraft, the need to harmonize US regulation with international standards, and the statutory deadline expressed in the FAA reauthorization legislation “provide compelling justification to immediately adopt these changes,” the PHMSA said. The agency added that it will consider amending the interim rule based on the comments it receives.