The U.S. Department of Transportation has explicitly banned the use of electronic cigarettes, or vape pens, on commercial plane flights. The rule applies to all scheduled flights in, to, and from the U.S.

“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,” Transportation Secretary Anthony 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.”

The restriction will be formally published in the Federal Register, clarifying current regulations that ban smoking of tobacco products. The regulation doesn’t clearly state what falls under the “smoking” ban, though the DOT considered it broad enough previously to include no use of e-cigarettes on planes. Hover, there was still some lingering confusing over vaping.

There’s some evidence that e-cigarette aerosol can contain harmful chemicals, and the DOT wants to ensure that all passengers are able to avoid any potential harm within the confined space of an airplane. The ban includes electronic cigarettes in all forms, including “electronic cigars, pipes, and devices designed to look like everyday products like pens,” the DOT said.

Passengers are also not allowed to carry battery-powered portable electronic smoking devices in checked package or charge the devices onboard an aircraft, according to the DOT’s Pipeline and Hazardous Materials Safety Administration.