Firefighter Michael McGuire rushed from room to room on the 11th floor of the Norman Blumberg Apartments high-rise, making sure residents were out, when his air pack ran out.
His team members noticed that he fell down during yesterday morning's fire and went into rescue mode, rushing him down the stairs to paramedics, Fire Commissioner Lloyd Ayers said.
Last night, McGuire, 40, married with a young daughter, remained in critical but stable condition at the Hospital of the University of Pennsylvania.
He has been undergoing treatment in a hyperbaric chamber, which pumps oxygen into him.
Ayers said he was not sure whether McGuire hadn't heard the warning signal that his air was low, or whether it had failed to beep. The Fire Marshal's Office will test his gear, he said.
McGuire comes from a family of firefighters. His brother John is a lieutenant, and their father, the late John McGuire, was a battalion chief.
Mayor Nutter, who visited McGuire at HUP with Ayers and others, said McGuire is with Engine 27 but was detailed to Engine 13, near 15th and Parrish streets, one of the companies that responded. The 5 1/2-year firefighting veteran previously worked in the Police Department.