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Julie Brewer already detects smoke in the air.
"Yes, just slightly," said the San Francisco resident. "I do smell the smell of smoke."
A team of 25 at the Bay Area Air Quality Management District says the smoke from the Kincade Fire will arrive Thursday evening and early Friday, propelled by northeasterly winds. However, don't be fooled into thinking it takes visible smoke to pose health hazards.
VIDEO: SKY7 captures huge plume of smoke from Sonoma County wildfire
"Particulate matter pollution is invisible to the naked eye," said Sarah Zahedi, a district public information officer. "Because those particles are so small that they can bypass your lungs' natural defense systems. So just because you can't see the smoke doesn't necessarily mean you won't be impacted."
Children, seniors and people with asthma are the most vulnerable, according to Dr. John Balmes, a specialist in pulmonary critical care at UCSF. He recommends that people should stay indoors when it's smoky, avoid outdoor exercise and use air filters.
VIDEO: Sonoma County woman caught on camera trying to save home from fast-moving wildfire
When people exercise they tend to breathe through their mouths, he said, which allows more particulate matter to enter the lungs. Erin Belshaw and Jonathan Gall endured the smoke from the wildfires over the past two years.
"I just remember it was hard breathing," Gall said. "It really irritated the lungs." To ease the discomfort, he said he wore a face mask.
However, Dr. Balmes says he has changed his mind about everyone wearing N95 face masks. He says there is little evidence they help healthy adults. Still, using them doesn't hurt.
Heads Up, Bay Area! Although the #KincadeFire isn't causing smoke issues over the Bay Area today, shifting winds tomorrow will likely cause the smoke to be directly over much of the region. Impacts to SFO may begin as early as 11am Friday. pic.twitter.com/3tlCIXIC5r— NWS CWSU Oakland (@NWSCWSUZOA) October 24, 2019
"They handed them out at our office the last time," said Belshaw, "So we still have them from the first time it happened."
The Air Quality Management District will be monitoring the particulate matter in the air throughout the nine Bay Area counties.
Get the latest developments on the Kincade Fire here.