Five other firefighters were also hospitalized for injuries sustained fighting the fire.
The first 911 call came in at 12:25 a.m. when neighbor Tony Sawmut was awakened by his cat.
"I jumped out of bed and seen this place here, the flames they were about 20 feet high, then I called 911," Sawmut said.
Firefighters responded three minutes later to the vacant two story house that was fully engulfed by extremely hot, fast moving flames.
The fire started low, but within minutes it worked itself up to the attic.
A third alarm was called 13 minutes after firefighters first responded. By that time, 117 firefighters were battling the blaze.
"The back third of the building collapsed into the structure and when it did it sent all the super-heated gases and the flames right into where the firefighters were fighting the fire in the hallway in the front bedroom," San Francisco Fire Department Deputy Chief Pat Gardner said.
Six firefighters were taken to the hospital with injuries ranging from burns to smoke inhalation.
The most seriously injured, an 11 year veteran firefighter, is fighting for his life at San Francisco General Hospital where he is listed in critical condition with major injuries to his lungs.
"I'm told the first 48 hours to 72 hours are critical in assessing how the road will go from there but he's with family members and he's with our members," San Francisco Fire Department Chief Joanne Hayes-White said.
The arson task force is investigating the cause of the fire.
