There was now no doubt that the reactor was on fire, and had been for almost 48 hours. Reactor Manager Tom Tuohy donned full protective equipment and breathing apparatus and scaled the 80-foot (24-m) ladder to the top of the reactor building, where he stood atop the reactor lid to examine the rear of the reactor, the discharge face. By doing so, he was risking his life by exposing himself to a large amount of radiation. He reported a dull red luminescence visible, lighting up the void between the back of the reactor and the rear containment. Red hot fuel cartridges were glowing in the fuel channels on the discharge face. He returned to the reactor upper containment several times throughout the incident, at the height of which a fierce conflagration was raging from the discharge face and playing on the back of the reinforced concrete containment — concrete whose specifications required that it be kept below a certain temperature to prevent its collapse.