People take pictures of the Golden Gate Bridge as smoke from wildfires covers the San Francisco skyline Tuesday, Oct. 10, 2017. Eric Risberg/AP The smell of fire hangs in the air in San Francisco. Despite being located more than an hour's drive from the epicenter of what is being called one of the worst firestorms in state history, the breeze here blows heavy with soot.

Office workers wearing face masks crowd the streets. The area's homeless — who have no choice but to be outside — break out regularly into spates of coughing.

And it's showing no signs of clearing.

"Smelling the wildfire smoke in San Francisco? It's moving back in. Air quality worsening," Daniel Alrick, a meteorologist for the Bay Area Air Quality Management District, tweeted around noon on Friday. He said conditions will persist — and may worsen — through the weekend.

On Thursday morning, the Environmental Protection Agency's air quality index for the Bay Area was 160 — higher than Beijing's reading for the same time and day of 122. It is classified as "unhealthy" and is a level 4 out of 6, with 1 being "good" and 6 being "hazardous."

On Friday, the air quality worsened, as it is expected to continue to do for the next several days. In parts of the area, particularly those locations closer to Sant Rosaa and the fire epicenter, the air quality slid into the "very unhealthy" category — a level of 5 out of 6. The EPA's message to residents is clear: "Everyone ... should reduce prolonged or heavy exertion," especially "people with heart or lung disease, older adults, and children."

In and around wine country in Santa Rosa and Napa Valley, strong, dry winds helped unite what began as a string of separate fires, pulling the blazes across swaths of fields and freeways. Officials estimate that more than 2,000 homes, businesses, and other structures in eight counties have now been devastated by the fires. At least 29 people are dead, and the death toll is expected to rise as rescue workers clear through the rubble. More than 460 people have been reported missing in Sonoma County.

The same currents are also spreading the dirty air across the Bay Area — in some cases all the way from wine country to the South Bay. People across the state are breathing in unhealthy air, putting people with asthma and other respiratory conditions at particular risk.

“We are reporting the worst air quality ever recorded for smoke in many parts of the Bay Area,” Tom Flannigan, a spokesman for the Bay Area Air Quality Management District, told the East Bay Times. “This is similar to what you see in Beijing, China in bad air days there.”

High soot readings, also known as particulates or PM2.5, are of the most concern to regulators. As of Wednesday afternoon, those levels are currently “very elevated," Kristine Roselius, a spokesperson for the Bay Area Air Quality Management District, told SF Gate.

That pollutant is known to be harmful because of its ability to penetrate and lodge deep inside the lungs, where it can worsen respiratory issues and trigger asthma attacks.

Officials advise people in the area to stay indoors when possible and possibly leave the area until the forecast improves.

"Air quality is expected to remain unhealthy into the weekend as northerly winds are forecast to continue bringing smoke into the area," said Alrick.

This map shows the counties affected by the firestorm and where some of the fires are burning, as of 5 PM ET (2 PM PT) on Thursday. Scroll over the map to see county names.