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.

Southwest says it will limit battery charging to devices that are easily visible, in case chargers catch fire.

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.