Apple recently issued a warning on its support page “Important iPhone Safety Information” reminding users never to charge an iPhone under a pillow or blanket. The warning says, “Never sleep on a plugged device, power adapter, or wireless charger, or place them under a blanket, pillow, or body. Place your iPhone, power adapter, and any wireless charger in a well-ventilated area while using or charging. Be especially careful if your body experiences conditions that affect your body's ability to perceive heat.”