Fantasia Barrino Burned Arm in Tour Bus Vaporizer Accident

Fantasia Barrino suffered 2nd degree burns to her arm when she knocked over a vaporizer in her sleep ... TMZ has learned.

Sources close to the singer tell TMZ ... she was dozing on her tour bus Sunday with an aromatherapy vaporizer nearby. She uses it to soothe her vocal cords. We're told she thinks she rolled over onto the machine's cord, which caused hot water to spill out on her right forearm.

Our sources say Fantasia was alone on the bus when the accident occurred -- everyone else was inside the Memphis venue getting ready for the show that night. We're told the burns were bad, but docs removed the damaged skin and expect her to heal fully ... without surgery or permanent scarring.