Firefighters were again hampered when it was discovered the pressure relief valves on the standpipes were improperly adjusted when installed in the building. The Philadelphia Fire Department nozzles allowed nozzle pressure while One Meridian Plaza's pressure relief valves were giving less than discharge pressure, which was not sufficient to fight the fire. It was several hours into the fire before a technician who could adjust the valves arrived at the scene. The area around the building was cleared of pedestrians and firefighting personnel because of falling glass and debris. The falling debris was dangerous for firefighters because they often had to cross the perimeter around the building to enter and leave the high-rise. Hose lines stretched into the building were damaged by falling debris and one firefighter was struck by debris and seriously injured while tending to the lines. During the second hour of the fire it spread onto the 23rd and 24th floors. Heavy smoke was building up in the stairwells and a captain and two firefighters from Engine 11 were assigned to go to the top level to ventilate the stairwell. The three firefighters went up a center staircase from the 22nd floor and soon radioed that they were disoriented by heavy smoke on the 30th floor. There were attempts to direct the firefighters through the radio, and soon after the captain requested permission to break a window for ventilation, which was followed by a message that the captain was down. Permission to break the window was given and a search and rescue effort was initiated. Search teams were sent from the lower floors and searched the 30th floor, but did not find the missing firefighters. The teams then moved onto the upper levels where one team got lost on the 38th floor and ran out of air in their self-contained breathing apparatus (SCBA). That team was rescued by a search team that had been placed on the roof by a helicopter. Rescue attempts continued until helicopter operations were suspended due to heavy smoke and thermal drafts caused by the blaze. Using a searchlight the helicopter crew searched the exterior of the building and at 1:17 AM February 23, the helicopter spotted a broken window on the 28th floor located in an area that could not be seen from the street. At about 2:15 AM a rescue team was sent to the spot and found the three missing firefighters unconscious and out of air in their SCBAs. The firefighters were taken to a medical triage set up on the 20th floor. There were attempts at resuscitation, but they were unsuccessful and the firefighters were pronounced dead. As the fire was going into its sixth hour it had spread up to the 26th floor.