Heise gauge dropping, an attempt was made to isolate the divers from the leak by sealing the door of the entrance lock that led to the bell, but according to the dive log this effort was "abandoned." To protect Holmes and Baldwin from further pressure loss, the supervisor ordered them to climb into chamber one. There, they leaned against the inside hatch while the supervisor injected a small amount of helium inside the chamber to seal the door. At this point, the supervisor forgot to reset the valves to reconnect the Heise gauge with chamber one. Because chamber one was not equipped with a dedicated depth gauge, Holmes and Baldwin were now in a part of the system not being monitored by any gauge. Meanwhile, the Heise gauge was still recording a pressure drop, which the supervisor erroneously believed was reading chamber one. He thought that he had failed to achieve a seal on chamber one's hatch, and so he began to feed large quantities of pure helium into the chamber where the two divers were stationed. By the time he realized his error, Holmes and Baldwin had been pressurized from to over the course of several minutes. The rapid compression, combined with the high thermal transfer property of helium, plus the high humidity factor of the atmosphere, caused the temperature of the atmosphere to rise from an estimated to . The two divers began pulling desperately on the chamber hatch to escape, but were unable to open the door. They took the mattresses off their bunks and lay on the somewhat cooler aluminum surfaces, but forced to breathe an intolerable atmosphere, the men died several hours later of hyperthermia. Fatal accident inquiry It was later pointed out by the presiding judge at the fatal accident inquiry that the way in which the diving system was designed and labeled, “especially as operated by Oceaneering, carried a high risk of human error, particularly during the distractions of an emergency.” Oceaneering's safety officer testified that the manner in which the control panel was plumbed “was a contributory cause” of the accident, and that it probably would not have happened had the panel for chamber one been equipped with a dedicated depth gauge permanently fixed for the purpose of reading only that chamber. Had there been such a gauge, then the supervisor would not have been misled by the Heise gauge, and therefore