Capt. Gabe Roder of the Vancouver Fire Department says the 46-year-old man was in the structure when the blaze broke out, apparently due to carelessly discarded smoking materials.
He says the garage has a self-contained living space and that the man managed to make it outside after flames erupted Tuesday night.
Roder says the man was on the ground when firefighters and paramedics arrived.
The man was treated at the scene before being transported to hospital, and Roder says he remains in critical condition.
The garage suffered extensive damage.