1. What is Surface Ozone? Ozone occurs naturally in Earth’s atmosphere wherever sunlight or chemical reactions break apart oxygen molecules (O 2 ) [O 2 ] + [O]  [O 3 ] Most of the ozone in the atmosphere is in the stratosphere, 8 to 50 km above the Earth’s surface –Screens out the most of the sun's harmful ultraviolet rays. Ozone near the surface is a problem –Reacts strongly with surfaces, including living tissue and inorganic structures.

2. Why Measure Surface Ozone Concentration? Ozone is a major product of air pollution and globally its abundance is unknown The amount of ozone present affects many other trace gases in the air Knowing the amount of ozone helps assess the degree to which it is an environmental problem

3. How to Measure Surface Ozone Use a chemical test-strip that changes color in the presence of ozone Expose the chemical test-strip to outside air for one hour Read the test-strip using a hand-held scanner The unit of measurement is a part per billion Cloud conditions, wind direction and current atmosphere temperature must also measured to help data interpretation Knowing relative humidity is helpful as well

4. Significant Values Average concentrations range from almost 0 ppb to over 150 ppb depending on time of year and geographic location In extremely polluted conditions ozone can reach 200 ppb and more Levels of surface ozone exceeding 80 ppb for 8 hours or longer are considered harmful for most living things