Driving Clean FAQs

What is ozone?

Ozone is necessary for life on earth, as we know it. In its proper place in the stratosphere (up high), ozone helps protect the earth from the sun's harmful rays. But on the earth's surface (down low), ozone is the major ingredient of smog, a problem plaguing many of our cities in Texas.

Ground-level ozone is formed when nitrogen oxides (NOx) and volatile organic compounds (VOCs) come together in the presence of heat and sunlight. NOx is found in the exhaust from motor vehicles and other sources of combustion or industrial processes. VOCs come from a number of sources, including evaporation tanks.

What is a nonattainment area and near-nonattainment area?

Three Texas areas are considered to be nonattainment, meaning they do not meet federal air quality standards because ozone pollution levels are too high: Houston/Galveston, Dallas/Fort Worth, and El Paso. However there are several more that are near-nonattainment or attainment-maintenance because they are close to exceeding federal air quality standards: Austin, San Antonio, Victoria, Tyler/Longview, Beaumont/Port Arthur, and Corpus Christi.

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

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

When is ozone season?

Summer months are considered to be ozone season because both heat and sunlight are abundant. Ground-level ozone is formed by chemical reaction when NOx and VOC emissions are exposed to heat and sunlight. The Texas Commission on Environmental Quality issues an ozone alert 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 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 positive reduction in the VOCs being released into the air.

I'd like to buy a cleaner vehicle. Where can I find out more information?

Check out EPA's online Green Vehicle Guide to help find the cleanest and most fuel-efficient vehicle that meets your needs.

Many of the major automobile manufacturers also have portions of their websites devoted to environmentally friendly hybrid or electric vehicle alternatives.

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. You also may qualify for vehicle repair or replacement assistance. Visit the AirCheckTexas Drive a Clean Machine website to find out more.

What can I do to maintain my car properly?

The best thing to do is to follow your vehicle manufacturer's maintenance recommendations.

  • Keep your car engine well maintained to lower exhaust emissions.
  • Change dirty air and fuel filters and regularly service the air conditioning.
  • Keep the correct pressure in your tires.
  • Seal your gas cap tightly, refuel during late afternoon or evening, and don't top off the tank.
  • Have your car regularly inspected and emissions tested.

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

No, Drive Clean Across Texas and Air Check Texas are separate state programs. Drive Clean Across 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 car, truck, or bus 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, by submitting an online reporting form on at smokingvehicle.org 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 contributing to air pollution by smoking excessively. 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 thru 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 half a minute or more.

How does "stopping at the click" reduce air pollution?

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. You can find out more about this clean air tip at http://www.epa.gov/donttopoff/.

Clean Air Tips