The dog, Susie, and its owner were visiting a friend at her 16th-floor apartment at a Fort Lauderdale high rise Friday when the incident happened.
Susie went to investigate an open closet inside the apartment, only to fall down an exhaust shaft.
Susie's owner, Elaine Caralis, said the vent was likely missing a panel that would have covered the drop.
Fort Lauderdale Fire Rescue pulled Susie out of the vent by cutting "holes above and below the second floor to try to get (to her)," firefighter Timothy Heiser said.
Caralis said the three-hour rescue was "heroic."
"I don't have children," she told CNN, "so Susie is my life, Susie is my family. They treated it like they were searching for a human being."
Veterinarian Dr. Spencer L. Ratnoff said it was a "miracle" Susie survived with no injuries other than some bruising.
"I'm thinking 15 stories, there are going to be multiple fractures, severe internal injuries or worse," he said. "I was worried it might need to be euthanized."