An employee was checking the inspection door to clean out any build up in the discharge chute. As the employee was heating the peanuts in the cooker to extract oil, he noticed embers and smoke in the discharge chute. The employee used a fire extinguisher to put out the embers and continued his work. As the employee opened the machine door next to the portal on the discharge chute, oxygen entered the chute and caused the peanuts to combust. A fireball shot out of the door and burned the employee's face, chest, and arms.