Portable chargers and power banks might be useful additions to your carry-on luggage, but they’re also a potential fire risk. Now Southwest Airlines is tightening rules around their use on board aircraft.

This year, there have been at least 22 incidents involving lithium batteries in air travel, according to data from the Federal Aviation Administration.

Passengers on Southwest Airlines flights will soon be required to keep their portable chargers in plain sight while using them due to concerns about the growing number of lithium-ion battery fires in a new policy that other airlines may adopt.