WALNUT CREEK (KPIX 5) — Much of the Bay Area continued to suffer under a blanket of wildfire smoke Thursday, even though the heavy burning from fires burning in the region is finished.

“I was at work last week and they told us to go home because the air quality was so bad,” said Kathryn Rugo, who was interviewed in Walnut Creek.

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The smoke can get stuck in your throat and burns your eyes, even indoors in some parts of the Bay Area.

“We missed work that day. It was so sad,” she said.

“I don’t think that our fires are putting out that much smoke anymore,” said Fire Captain Mitch Matlow, referring to the SCU complex fire. At 391,000 acres, it’s the second largest fire in state history. The fire is now 78 percent contained.

Matlow said what local residents are breathing now could be old smoke trapped in by Bay Area mountains.

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“It takes a while to push out all of that particulate matter. So smoke that was created a week ago is still sitting here,” explained Matlow.

With the heavy firefighting finished, crews are pushing in from the containment lines to put out hot spots which still put out large amounts of smoke.

It’s tedious, time consuming work that can’t be done with air tankers or water drops.

“You can’t get the water from a helicopter underneath the stump of a tree. You have to dig it out or let it burn and just watch it. Would a thousand gallons from a helicopter put out a large amount of fire? Absolutely, but it doesn’t do the overhaul, it doesn’t get into that hidden fire,” Matlow said.

And those hidden fires could smolder in spots for weeks.

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“There is a possibility that somewhere in there there will be a stump that will smolder until the rain finds it. Hopefully we will find it first and we will extinguish it,” Matlow said.