The U.S. Department of Transportation has banned the use of electronic cigarettes on commercial flights.

Transportation Secretary Anthony Foxx announced the new rule Wednesday, calling it an effort to prevent vulnerable passengers from being exposed to harmful chemicals. The measure applies to flights into and out of the United States, along with domestic and international carriers.

Previously, passengers were prohibited from packing the devices in their checked bags, but were allowed to bring them in carry-ons as long as the devices and batteries were not charged aboard the aircraft. It was unclear whether the previous rules prohibited inhaling from the vaporizers on flights, something DOT sought to clear up with Wednesday’s ‘final rule’.

The new rule effectively treats electronic cigarettes the same as traditional tobacco cigarettes, which are banned from use on U.S. flights.

“This final rule is important because it protects airline passengers from unwanted exposure to aerosol fumes that occur when electronic cigarettes are used onboard airplanes,” Foxx said in a statement. “The Department took a practical approach to eliminate any confusion between tobacco cigarettes and e-cigarettes by applying the same restrictions to both.”

DOT said the devices are a concern because they contain a number of harmful chemicals, potentially exposing children, older passengers and those with respiratory issues to aerosol in an enclosed space.

The department said the new rule eliminates any confusion over whether previous regulations applied to e-cigarettes, and it applies to all forms of electronic cigarettes including: electronic cigars, pipes and “devices designed to look like everyday products such as pens.”

The expanded ban also encompasses charter flights through domestic and international carriers that require a flight attendant to be on board.

In a statement Wednesday, Sen. Jack Reed (D-Rhode Island) praised the new measure, which is set to go into effect in one month. Reed, who has pushed the FDA to tighten its regulations on the devices, had been calling on the DOT to ban e-cigarette use on planes since 2014.

“Airline passengers and flight attendants should not be subjected to potential harm from e-cigarette secondhand exposure,” said Reed, the ranking member of the Appropriations Subcommittee on Transportation, and Housing and Urban Development. “And the new rule makes it less likely that these devices will spark an emergency.”

Reed joined Sen. Susan Collins (R-Maine) last year in asking DOT to finalize new rules on electronic cigarettes to minimize the fire hazard on flights. In his statement, Reed pointed to a January incident in which a Hawaiian Airlines flight was forced to emergency land when an e-cigarette stowed in a checked bag may have caught on fire.

In a congressional Committee on Transportation and Infrastructure meeting earlier this month, D.C. Del. Eleanor Holmes Norton proposed a ban on vaping on airplanes. The amendment, part of a more comprehensive aviation bill still working its way through congress, passed in the committee.

But not before Rep. Duncan Hunter (R-Calif.), an e-cig advocate, defiantly puffed on a vaporizer of his own. Hunter hailed the benefits of vaping, saying the activity has helped him quit smoking.

Rep. Duncan Hunter (R-Calif.) puffs on an e-cigarette during a congressional hearing.

Rep. Duncan Hunter (R-Calif.) puffs on an e-cigarette during a congressional hearing.

The congressman was concerned that Norton’s proposal would make travel more difficult for passengers flying with asthma inhalers and other kinds of medical devices. In its statement, DOT said its ban does not extend to devices such as nebulizers.

Hunter’s chief of staff, Joe Kasper, sharply criticized the DOT’s decision Wednesday, comparing vaporizers to any other battery-powered device.

“This Administration sees vaping as a proxy fight with tobacco, it’s that simple, when in actuality vaping is very different, as both a product and a preference,” Kasper said. “The point that vaping pens are a fire hazard is just a convenient excuse—because why not look at anything else with a battery, or anything else with a potential to ignite under extreme conditions.”

Norton said Wednesday she was pleased with DOT’s rule because it was not certain the FAA reauthorization bill to which her amendment was tied would pass. Norton said the devices are unsafe, citing a case last week when a man suffered severe burns after one of them exploded in his pocket.

“If such a fire occurred on an airplane, it could be catastrophic, which is why DOT had previously issued a rule (prohibiting) electronic cigarettes in checked baggage,” Norton said in a statement. “In any case, smoking was banned on airplanes more than 25 years ago.  I believe this case should have been closed long ago.”

A federal law banning smoking on all U.S. flights of less than six hours took effect on Feb. 25, 1990.