Firefighters battled the bitter cold to put the fire out inside the building on the 3800-block of South Ellis.
A 30-year-old victim suffered smoke inhalation according to the Fire Department.
Update 3809 S Ellis all companies have picked up from the scene. Office of Fire Investigations (OFI) investigating. There were 10 displacements noted.— Chicago Fire Media (@CFDMedia) February 14, 2021
The man was taken to the University of Chicago Medical Center in critical condition, fire officials said.
The blaze was put out by about 3:40 a.m., according to fire officials.
The cause of the fire is now under investigation.
The Sun-Times Media Wire contributed to this report.