Brush fires burning in Napa, Sonoma, Lake and Mendocino Counties have triggered dangerous air quality in the Bay Area.Air district officials say strong winds have blown the smoke from the fires, which have burned tens of thousands of acres, throughout the Bay Area.Residents are advised to limit outdoor activities and to set air conditioning and car venting systems to re-circulate to prevent outside air from entering.Elderly people, children and those with respiratory illnesses are particularly susceptible to the smoky conditions and should take extra precautions, air district officials said.