Plumes of smoke from wildfires have turned blue skies gray and led to concerns over air quality, but ozone levels have yet to spike to dangerously high levels.

The Utah Division of Air Quality urged people Thursday to keep it that way by refraining from driving as much as possible.

With temperatures nearing 100, regulators issued the voluntary air action to help reduce the buildup of smog.

Both Salt Lake and Davis counties are under the no-action advisory and are surrounded by a triangle of the state’s four largest and most active wildfires.

To the north are the State and Millville fires, which collectively have burned more than 28,000 acres. The State Fire started west of Portage in Box Elder County and has burned north into Idaho, while the Millville Fire is burning in Cache County east of Hyrum.

Both Box Elder and Cache counties had air quality termed as moderate. To the west of Salt Lake City is the Patch Springs Fire in Tooele County’s Skull Valley, which has burned 13,000 acres. And on Salt Lake’s eastern flank, on the other side of the Wasatch Mountains, the Rockport Fire has burned nearly 2,000 acres and destroyed eight homes.

The smoke that hangs in the air and can be seen for miles has prompted people to pepper the division with questions or concerns.

Donna Kemp Spangler, spokeswoman for the Department of Environmental Quality, said as ugly as it may look out there, the smoke from the wildfires has not pushed valley ozone levels beyond the federal threshold of 75 parts per billion.

“The numbers are saying one thing, but many members of the public aren’t buying it,” Spangler said. “They walk outside and they can smell the smoke and their eyes sting, but we are not seeing the high hits.”

Ash blown around by the blazes has been deposited on cars in the Salt Lake Valley and is unappealing, but Spangler said it isn’t a health quality concern.

The wildfires’ smoke is driving up particulate matter — which is different from ozone — with the division warning that the smoke could cause high concentrations in populated areas. People with existing heart ailments should reduce physical exertion and outdoor activity, state air quality officials said.

Spangler said people should exercise common sense and refrain from going outdoors if they are bothered by the smoke. Sensitive populations, such as the elderly or very young, should also limit their exposure, she said.

The Wasatch Front and the western half of the state remains under a red flag warning by the National Weather Service in Salt Lake City, which means fire danger is at a critically high level.

Extremely low humidity coupled with near record high temperatures are combining to create the dangerous conditions, which are complicated by gusting winds and dry thunderstorms.

All of the four major fires burning in Utah have been started in the past week by lightning strikes.

via Smoke fills Utah skies; air quality remains moderate | Deseret News.