SONOMA, Calif. — Some of the worst wildfires ever to tear through California have killed 31 people and torched a vast area of the state’s north this week, but the reach of the blazes is spreading dramatically further by the day, as thick plumes of smoke blow through population centers across the Bay Area.
Everything now smells burnt. Hills and buildings are covered in a haze. Residents nowhere near the front lines of the fires now venture out wearing air masks. On a hillside above the Russian River, a broad and menacing band of fire is turning a blue sky into a gray miasma of soot.
Air-quality, based on levels of tiny particles that can flow deep into the lungs, is rated “unhealthy” across much of Northern California, and smoke has traveled as far as Fresno, more than 200 miles to the south. The effects are many: schoolchildren are being kept inside during recess, the Oakland Raiders canceled their outdoor practice on Thursday to prevent players from breathing in the bad air, and doctors are reporting an increase in visits and calls from people with lung and heart trouble.
It is the 31 deaths, however, a toll that surpasses the official number of people killed by the single deadliest wildfire in state history, that has horrified Californians. The Griffith Park fire of 1933, in Los Angeles, killed 29 people despite burning a mere 47 acres, according to officials.
Late Thursday, the authorities said they had identified 10 of 17 people who were killed in Sonoma County. Most were in their 70s and 80s, and most were found in houses. One was found next to a vehicle.
“We have found bodies that were nothing more than ash and bones,” said Robert Giordano, the Sonoma County sheriff. In some cases, he said, the only way to identify the victims was by the serial numbers stamped on artificial joints and other medical devices that were in their bodies.
Because the fires have sent so many residents scrambling for safety, separating them from relatives, the authorities have received reports of 900 missing people and have deployed 30 detectives to track them down. Officials said they had confirmed the locations and safety of 437 people and were still looking for the other 463.
If they cannot find them by phone or online, they send search and rescue teams with cadaver dogs to the homes — if the homes are accessible, which in many cases, they still are not.
“It’s going to be a slow process,” Sheriff Giordano said.
Statewide, there were 21 major fires still burning on Thursday, which had consumed more than 191,000 acres since the outbreak began on Sunday night, said Ken Pimlott, the chief of Cal Fire, the state firefighting agency. The number of separate fires rises and falls often, as new blazes flare up and old ones merge, but the size of the devastated area has grown steadily.
Underscoring the vast scale of the crisis, a line of fire that appeared to span at least two miles descended into Alexander Valley, a wine grape growing region in Geyserville along the Russian River. Thick white columns of smoke poured from the forested hillside above the vineyards as the fire crept down into the valley.
Health officials were particularly focused on young children, who are at a higher risk than adults from dirty air. They breathe faster and take in more air than adults because they run around more. They also have smaller airways, so irritation in those narrower pipes is more prone to cause breathing trouble.
“People with pre-existing heart and lung disease, the elderly and young children should stay in the house with the windows closed,” said Dr. John Balmes, an expert on the respiratory effects of air pollutants at the University of California, in both Berkeley and San Francisco.
Certain masks can filter out fine particles, but surgical masks are useless, and so are the ones used to protect against big particles. The masks that work are a type called N95, available in many hardware stores.
Nancy Barkley, 40, a nurse from Indiana who is on a 13-week assignment unrelated to the fire emergency, drove dozens of miles from Santa Rosa to find face masks.
“I kept on driving because they were out everywhere,” she said, pulling down her surgical mask to talk.
Northern California is accustomed to wildfires and occasional wafts of smoke that drift with the winds. But nothing like this.
“I’ve lived here 50 years — I’ve never seen it this bad,” said Paul Ackerley, a 90-year-old World War II veteran.
Mr. Ackerley was walking through his neighborhood Wednesday when a woman stopped her car and offered him a mask.
People closest to the fires have the greatest risk of health problems. There, heavy smoke can include toxic substances emitted when man-made materials burn. Plastics can release hydrochloric acid and cyanide.
“Smoke inhalation can kill you,” Dr. Balmes said. “There’s no doubt about that, but it’s all dose-related. If you breathe in a lot of smoke from any fire, especially a fire in a building with man-made materials that can emit these toxins, you basically have chemical burns of the airway.
“Just like your skin can slough off when it’s burned, the airway lining can slough off. It can be life-threatening. People have to be intubated and put on a ventilator,” he said.
Hospitals near the worst fires are struggling as they continue to take in patients.
At Santa Rosa Memorial, the city’s largest hospital, technicians installed a large air filtration system to clear smoky air from the hospital lobby. The hospital has handled 130 fire-related cases since Sunday night, when the fires began. Bus drivers in the city have been issued face masks.
“We’ve seen patients who have chronic lung disease, like emphysema, generally older patients, which is really exacerbated by the smoke,” said Dr. Chad Krilich, chief medical officer for St. Joseph Health, which includes Santa Rosa Memorial, another hospital and other facilities in Sonoma County.
“For some of them, it’s really life-threatening,” he said, adding that patients even without asthma or other lung problems are coming in with breathing trouble. Most are being treated in the emergency rooms, which would normally see 105 to 135 patients a day, but are now seeing 150 to 180 a day.
Their inpatient count rose at first, but they have been transferring patients elsewhere, “because we are at risk of evacuation, too,” Dr. Krilich said, adding, “We know at least 108 of our employees are homeless, and 46 others have had to evacuate.”
Steve Huddleston, vice president for public affairs of NorthBay Healthcare, said the network has two small hospitals and three outpatient clinics in Solano County, east of the fires. One of its outpatient clinics is less than a mile from the fire line, but still operating.
In the emergency rooms and the clinics, he said, “we’re seeing 100 patients a day with respiratory distress and asthmatic attacks from the smoke.”
Many have chronic lung disease or asthma, but not all.
“All of our beds are full, and they have been for two days,” Mr. Huddleston said.
He added: “We’re on the edge of feeling overwhelmed. The staffing is becoming challenging. We’ve had half a dozen of our physicians or staff members lose their homes in the fires. We have staff members who live in the evacuation zones, and they’re trying to get their belongings and their loved ones out of there.”
In areas directly affected by the fires, many schools have canceled classes for the week, leaving parents scrambling.
On Thursday, William Roman, 13, a middle-school student, was helping his grandfather in a landscaping job at a strip mall in Santa Rosa, watering plants — with a face mask on.
“If we’re going to play outside we need to wear a face mask — that’s what my mother says,” William said.
Depending on the winds, the smoke can range from heavy to none. In parts of Santa Rosa on Thursday, there was something resembling a blue sky. Yet even when the smoke was not visible, the outdoors smelled like a fireplace.