A cozy fire in the fireplace won't be a backdrop for this morning's Thanksgiving Day football games as bad air quality has health officials putting a damper on wood-burning throughout most of the Rogue Valley.

A cozy fire in the fireplace won't be a backdrop for this morning's Thanksgiving Day football games as bad air quality has health officials putting a damper on wood-burning throughout most of the Rogue Valley.

Jackson County environmental health officials tapped today as a "yellow" air day, meaning the only wood-burning allowed in the so-called Air-Quality Maintenance Area is in certified stoves that emit no visible smoke.

Burning in non-certified stoves and fireplaces will be banned beginning at 7 a.m. today and will remain banned for the immediate future.

"Isn't that something?" said Gary Stevens, the county's environmental health program manager. "Talk about bad timing for the holiday."

The "yellow" status was expected to remain through the weekend, Stevens said.

The county every morning will update its woodstove advisory hotline at 776-9000.

The culprit is a cold air mass hovering over the Rogue Valley, where theU-shaped bowl of mountain ranges can trap bad air. The poor ventilation allows airborne particulate matter, such as small particles in wood smoke, to accumulate and linger in the air. When the particulates reach and remain above unhealthy levels, air-quality managers ratchet down woodstove use.

This past week, measurements taken by the state Department of Environmental Quality show distinct spikes in airborne particles in the early evenings and again in the mornings.

"So we know it's woodstoves," Stevens said.

Shifts in weather — particularly windy storm fronts — typically are needed to flush the valley's air.

The ban on non-certified woodstove use was set just for today, but more bad-air days are expected, Stevens said.

"After Thanksgiving, it's unknown," Stevens said. "We were expecting some winds, but they never materialized."

Reach reporter Mark Freeman at 776-4470, or e-mail mfreeman@mailtribune.com.