Drive Clean Texas

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Driving Clean FAQ

What is a nonattainment area and near-nonattainment area?

Nonattainment and near-nonattainment areas are areas of the country where air pollution levels persistently exceed or are near exceeding the national ambient air quality standards set by the U.S. Environmental Protection Agency.

Learn more about nonattainment and near-nonattainment areas in Texas.

The air looks pretty clean to me. What's the problem?

While some emissions are visible along skylines as a haze or yellowish fog, many emissions are clear. The U.S. Environmental Protection Agency has identified pollutants, many of them invisible, which contribute to ground-level ozone (smog).

What is ground-level ozone?

Ground-level ozone is not emitted directly into the air, but is formed when nitrogen oxides (NOx) and volatile organic compounds (VOCs) come together in the presence of sunlight.

When is ozone season?

Summer in Texas is considered to be ozone season due to slow wind speeds and sunny hot days that create conditions where ground-level ozone can form. The Texas Commission on Environmental Quality issues ozone alerts on days when weather conditions are expected to be conducive to producing high levels of ozone pollution.

Why are drivers told to fill up early in the morning or in the evening when ozone levels are high?

Filling your gas tank during cooler morning or evening temperatures means less ozone formation—especially during the summer ozone season. When temperatures are cooler, gas is denser and evaporates less. Evaporation of gasoline releases VOCs (volatile organic compounds) into the air, which can contribute to smog and other air quality issues. The amount released while filling one tank isn't much, but when you multiply that by the millions of drivers on the road in Texas, every time they fill up, this easy small change can amount to a reduction in the VOCs being released into the air.

Where can I find out more information on cleaner vehicles?

Check out EPA's online Green Vehicle Guide to help find clean and fuel-efficient vehicles.

I can't afford a new car, and I can't drive any less than I do. What can I do to improve the air in Texas?

The good news is that you're probably already taking the most important step—maintaining your vehicle according to manufacturer's specifications. If you're not, this is a simple step you can take to make your car last longer, perform better, and likely get better gas mileage. By keeping your vehicle in proper running condition, you ensure the best chance for your vehicle to run as clean and efficiently as possible.

What can I do to maintain my car properly?

Follow your vehicle manufacturer's maintenance recommendations in your owner's manual.

Does the Drive Clean Texas campaign run the state Inspection and Maintenance program or the Air Check campaign?

No, Drive Clean Texas and Air Check Texas are separate state programs. Drive Clean Texas is an air quality public education and outreach campaign focusing on vehicle emissions. Air Check Texas supports the state's Inspection and Maintenance program. The campaigns are linked by their emphasis on improved vehicle maintenance, which ultimately benefits our air.

I have noticed vehicles on the road with excessive smoke coming from their exhaust. How can I report a smoking vehicle?

The next time you see a vehicle anywhere in Texas with dirty smoke coming from its exhaust for more than 10 consecutive seconds, write down the license number, date, time, and location you saw the smoking vehicle. Report the smoking vehicle, within 30 days, at or by calling 1-800-453-SMOG (7664). You do not have to give your name, and the report is free.

The Texas Commission on Environmental Quality (TCEQ) will then notify the owner in writing that his or her vehicle may be excessively releasing emissions. The TCEQ will also provide the owner with information about how car maintenance will improve the vehicle's performance.

Can parking and walking inside rather than going through the drive-thru really help clean up the air?

Yes, idling wastes gas, damages pollution control equipment on your vehicle, and produces carbon monoxide—an invisible, odorless, poisonous gas. In fact, turning off the car and starting it again uses less gas and produces less carbon monoxide than idling for thirty seconds or more.

How does "stopping at the click" help keep our air clean?

We recommend stopping at the click when you fuel your vehicle because overfilling your tank releases harmful fumes into the air. Also, you need extra room in your gas tank to allow the gasoline to expand. If you top off your tank, the extra gas may evaporate into your vehicle's vapor collection system.