I make a point to charge my lipo's on a glass top oven usually without a bag. If it were to go off, there's nothing to burn. However the toxic smoke will still be present as it would if a bag were used anyway. If you think about it, many items use lithium batteries inside of the home: laptops, personal shavers, tooth brush, game controllers, ect, everything seems to have battery that could potentially go bad at any moment.