SALT LAKE CITY -- The air pollution that smothered mountain valleys in northern Utah for more than a week has made a dramatic improvement.
Regulators say the toxic smog could return within days, however, and they are keeping a ban on wood-burning in place.
Regulators say they are acting more quickly ahead of Utah's periodic but intense air pollution inversions. Even on a day when the air is clear, they are banning the use of fireplaces when they expect pollution to build up again. Regulators say wood smoke can linger in the air for days.