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What goes into determining a burn day?

How does the Oregon Department of Environmental Quality or Jackson County make the determination on which days are a green or yellow or red day (for burning)? Thanks for your assistance.

— Jim P., Medford 

Always happy to be of assistance, Jim. It's what we're here for. 

As you know, a green day means utilizing wood stoves and fireplaces is fine on that particular day because of the air quality. On yellow and red days, it's not. Yellow means the air is "approaching" unhealthy levels, according to the county's public health website, and red means it's already there. 

As to which color any given day is going to be, that actually goes to Jackson County's Environmental Health division.

Chad Petersen, program manager for the agency, says the Oregon DEQ has data on levels of fine particulate matter — or pm 2.5, a ridiculously tiny pollutant particle (you could line up 10,000 of them in an inch-long space) — in the air. 

"We look at the past and present of the data, and then we take an average of the most recent 24-hour numbers," Petersen says. 

But it doesn't stop there. Health officials also look at trends and the weather forecast over the next few days. 

"If they're calling for an inversion, kind of what the weather forecast is going to be, the predicted ventilation index, whether it's a burn day or not a burn day, all of those things."

It's a lot to look at, but Petersen says the pm 2.5 levels are the biggest factor.

"It's not an exact science. There are a lot of things that got into trying to predict these things," he says.

For more information, you can look at the county's wood burning particulars on their environmental health website, http://jacksoncountyor.org/hhs/Environmental-Public-Health/Wood-Stove-and-Open-Burning/Wood-Burning-Advisory.

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