Tom Smart, Chopper 5, Deseret News
An inversion of smog hangs over the valley on Dec. 2, 2010, in Salt Lake City. On Tuesday, The Utah Department of Environmental Quality issued a red air alert for Salt Lake and Davis counties on Tuesday.

SALT LAKE CITY — State environmental officials are advising northern Utah residents to avoid unnecessary driving or burning.

The Utah Department of Environmental Quality issued a red air alert for Salt Lake and Davis counties on Tuesday.

That means the air quality is bad enough that officials are calling for those with respiratory or heart disease, the elderly and children to avoid prolonged or heavy exertion outdoors.

Yellow alerts have been issued for Weber, Box Elder, Tooele and Cache counties.

Residents are asked to drive as little as possible during yellow and red days because cars contribute significantly to the area's air pollution.

A yellow alert is one level short of a red alert, which prohibits wood burning.