The US Department of Transportation and Federal Aviation Administration are banning people from storing lithium ion cells or batteries as cargo on passenger planes, the agencies announced today. Companies also cannot ship batteries with more than 30 percent charge aboard cargo-only aircrafts.

This doesn’t affect most consumers outright — you can still bring your spare batteries and gadgets aboard in a carry-on bag. But people who buy batteries online might be affected. Phones, external batteries, and electronic devices in general will no longer arrive with a full charge, so as to avoid the risk of fire or explosion that could damage aircraft while in flight.

Lithium ion batteries pose a fire risk

In 2017, the FAA urged the global airline community to reconsider allowing batteries on flights because of the fire risk. The FAA conducted 10 tests in which it packed a fully-charged laptop into a suitcase and tested various scenarios in which the battery could catch fire. One example was an aerosol can of dry shampoo being strapped to the laptop. A fire immediately started, and the can exploded within 40 seconds.

Months before that study, the Department of Homeland Security banned tablets and laptops from eight Muslim-majority countries, but in that case, it required people to check their batteries as opposed to bringing them aboard in a carry-on. The decision related to concerns over explosives making their way onto the plane.

Most infamously, airlines banned passengers from bringing a Samsung Galaxy Note 7 on a commercial flight because of its battery malfunction that led to the device catching fire and in some cases exploding.