Protect your fellow San Antonians on Ozone Action Days

We all enjoy this wonderful city and all it has to offer, but to keep enjoying it we need to do our part to keep San Antonio beautiful. One way is to keep your eye out for Ozone Action Days. These events are announced frequently between March and November, when the sunlight tends to be the strongest. In fact, there is an Ozone Action Day set for Friday, April 26.

The Texas Commission on Environmental Quality (TCEQ) notifies the Alamo Area Council of Governments (AACOG) when an Ozone Action Day is in effect. This is an orange-level alert, which means that air quality is predicted to be unhealthy for young children whose lungs are still developing, and for those who work or exercise outside for extended periods of time. 

You should know what O2 is because it’s the compound that keeps us all alive—oxygen. But what is O3? This gas, also known as ozone, is essential to our survival, but it’s definitely not for breathing. Up in the stratosphere it’s made naturally and absorbs harmful ultraviolet rays from the Sun. But high ozone levels at lower altitudes—what we call ground-level ozone is a toxic atmospheric pollutant.

Ozone is not emitted directly into the air by any one pollution source but is formed through chemical reactions between natural and man-made emissions and nitrogen oxides (NOx) in the presence of sunlight. These gaseous compounds mix in the air, and when they interact with sunlight, ozone is formed. These pollutants can come from automobiles, gas-powered engines, refineries, chemical manufacturing plants, solvents used in dry cleaning and paint, and wherever natural gas, gasoline, diesel fuel, kerosene, and oil are used as fuel.

Stay informed about Ozone Action Days by following us on Facebook and Twitter. You’ll see the Ozone Action Day graphic in the feed.

Here are six things you can do on Ozone Action Days:

  1. Sign up for Ozone Action Day alerts. The first step toward change is awareness. Go to to have an alert sent to you by email or text.
  2. Don’t idle. Pollution from cars (oxides of nitrogen, NOx) produces ozone and contributes to air pollution. Don’t let your car idle when picking up children at school. Go inside instead of using the drive-thru.
  3. Fill up after 6 p.m. If you must fill up your car, do it after 6 p.m. Gasoline is made of VOCs that contribute to ozone formation in the presence of sunlight.
  4. Use mass transit. On ozone action days, use VIA buses, carpools, or other mass transit. This will reduce the number of vehicles in traffic and reduce congestion.
  5. Bring your lunch to work. Bringing your lunch will eliminate a vehicle from being on the road during the time of day that sunlight is most intense and most likely to create ozone.
  6. Postpone lawn work. Do not use gas-powered lawn equipment on Ozone Action Days. If you do have to work on your lawn on an Ozone Action Day, wait until after 6 p.m.

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