A sprinkler system and quick response by firefighters limited damage from a fire to an office building Saturday in San Diego, authorities said. At about 5:15 p.m. a passerby noticed flames coming from the side of a building at 9449 Balboa Avenue, fire officials said. It went to a second alarm at 5:31 p.m. and the flames were out within 20 minutes. Fire damage was confined to the third floor exterior deck and water damaged a couple of law offices next to the deck, firefighters said. No injuries were reported, they said. The fire was caused by discarded smoking materials, officials said.