When fire crews arrived on the scene, near 19th Avenue and Cactus Road, flames had already spread into neighboring units.
They were able to contain the fire to one unit, with minimal damage to nearby homes, according to Captain Larry Nunez with the Phoenix Fire Department.
Nunez said the woman and a pet escaped the building without injury. He said they don't yet know if the home's smoke detector was working properly, but the incident is a good reminder for others.
"We always recommend that if citizens have a smoke detector in their home, they make sure it is in working order," he said.
Crews are still investigating the cause of the fire.