Smog is the common term for a mixture of atmospheric pollutants that appear as a gray or brownish-yellow haze. Ozone is the primary component of smog, but it is a colorless gas. Actually, it is small particulate matter that gives smog a hazy quality. These small airborne particles come from many sources, including industrial emissions, wind-blown dust from construction sites and roads, and vehicle exhaust.

Because ozone is the primary component of smog, many people associate high ozone levels with the familiar urban haze. However, the two don't always go hand-in-hand.

While a smoggy day often means that ozone levels are high, ozone may or may not be at hazardous levels. Likewise, we often see very high ozone levels when skies appear clear. Either one of these pictures could show a high ozone day!

The best way to know for certain whether or not we're experiencing high ozone levels is to check the Texas Commission on Environmental Quality's "Current Ozone Levels" map at http://www.tnrcc.state.tx.us/cgi-bin/monops/select_curlev.