Forces of Change

What Does Code Red Mean?

Code Red means that ground-level ozone levels are unhealthfully high. Children, older people, and people with chronic lung conditions should stay indoors.

On Code Red days, it’s smart to postpone buying gasoline or pouring gasoline into your lawnmower until after sundown. That’s because ozone forms when hydrocarbons like gasoline fumes mingle with sunlight and heat.

Aura Satellite

The Aura satellite measures the precursors of photochemical smog and tracks the movement of ozone in the atmosphere. It can determine the source of pollutants and provide advance warnings of potential Code Red days.

AURA Satellite Image
AURA Satellite Image
Ozone Chemical Formula
To a scientist, the atmospheric reactions that create ozone look like this.
Plant Leaf damaged by ozone levels
To a plant, ozone looks like this.
The spots on these leaves are damage caused by ozone exposure. Every bleached spot hampers the plant’s ability to grow through photosynthesis.
Specimen courtesy of Dr. Gretchen Smith, Department of Natural Resource Conservation, University of Massachusetts.
Photo by Siobhan Starrs © Smithsonian Institution
Person Caughing
To susceptible people, ozone looks
like this.
During an asthma attack, airways in the lungs constrict and fill with thick mucus, so that people with asthma can’t get enough air into their lungs. Asthma kills more than 5,000 Americans every year. Smog and smoke are asthma triggers. Some people attribute part of a three-fold increase in asthma in the past 20 years to increased air pollution, both indoors and out.
Photo © Archive Holdings, Inc./The Image Bank/Getty Images