Four months ago, the Department of Transportation banned e-cigs from being checked in baggage after a couple dozen fires and explosions. Now, the agency is taking another step toward safety by actually banning the devices from being used during flights.

The DOT unveiled the finalized rule on Wednesday officially banning the use of electronic cigarettes on all commercial and charter flights to, from, or within the United States.

While the agency believes that its previous regulations banning smoking on flights were sufficiently broad to include e-cigarettes, it revised the rules to explicitly define “smoking.”

“The Department took this action to eliminate any confusion over whether its ban includes electronic cigarettes,” the agency said in a statement.

The finalized rule treats electronic cigarettes, pipes, cigars, and other devices the same as tobacco cigarettes, which are also 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,” 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.”

Although further study is needed to fully understand the risks of electronic cigarettes, the DOT says it believes that a precautionary approach is best.

In October, the DOT announced rules prohibiting passengers and crew members from carrying any battery-powered portable electronic smoking devices (e-cigarettes, vaporizers, e-cigars, etc.) in checked baggage.

That rule also prohibited passengers and crew members from charging the devices or their batteries on aircraft.

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