While the smoke is worst along the Western Slope where the fires are burning, levels are also fluctuating on the Front Range.

Despite thick smoke in the sky today in southern Colorado, air quality alerts haven't been issued - instead they've been in the western slope. In fact - sometimes invisible compounds pose more risk.

Official air-quality results for Kyrene de la Sierra Elementary School show elevated levels of potentially harmful chemicals.

Allegheny County is increasing air quality monitoring after an explosion at a U.S. Steel plant south of Pittsburgh killed two ...

An air quality alert was reported by the National Weather Service on Tuesday at 12:17 p.m. in effect until 8 p.m. for ...