An employee was in the process of preparing a coal fired boiler section to be dumped. The employee stopped the coal feed to the section in preparation and as he approached the front of the boiler, the boiler went positive. In this instance, the door to the section that was being prepared to dump, blew open and the employee was blasted with a fire discharge. The employee received multiple first, second, and third degree burns to the arms, legs, torso, and face.