It is highly recommended to charge your Lithium Ion batteries inside of a LiPo safety bag.
The Lipo-Guard is a fireproof bag, designed to stop and contain the fire caused by incorrectly or poorly functioning lithium batteries, especially during charging. It is made from a fiberglass woven fabric, similar to fireproof suits worn by firefighters.
Batteries can fail, when they do it normally causes venting and sometimes fire. This bag will prevent flames from escaping and allow for venting so all you see is smoke.