Activity 3

Ozone in your Community

In this activity, students measure ground-level ozone levels in and around their school using a chemically treated paper. City smog is a serious global problem, and one worthy of investigation. 

ozone test strips

Test Strips to Measure Ground Level Ozone

You will need these materials for this inquiry:

Ozone test strips, graph paper, thermometers, psychrometers, Project Air Quality Recording Form. 

The image shows the tools for monitoring ground level ozone available from online. On the left is the kit which contains 12 ozone test strips, and a color chart (on the side of the bottle).  You should order the materials in advance of implementing Project Clean Air.

Ozone Observations and Measurements

In this activity you are going to study ground-level ozone in your local community. This might be the area around your school, or it might include various locations in your community. To do this you are going to set up some monitoring sites (for example your backyard, or a park near your house would be a suitable site), and then collecft data on ozone levels over a period of time. This will be decided upon in consultation with your peers and your teacher.

The picture above shows small strips of paper that have been treated with a chemical that will turn the paper a shade or purple or brown. Notice that the strip has two circles. The upper circle will react to ozone so that in one hour it turns a shade of violet, while the other circle will change color over an eight-hour period and turns a shade of brown. You will use a chart similar to the one shown below to interpret the ozone level when you do your experiments.

How the ozone test strips are used.

Tape the ozone test strips on a small index card. Since the chemical works when it is exposed to the air, you must work quickly.   After exposing the test strip compare the color change to the color chart provided on the bottle.

When you place the card in the monitoring location, you should record the temperature, humidity, cloud cover, cloud type, visibility, and weather. Use the Project Ozone Recording Form

Monitor ozone on school grounds or at home using the schedule you have agreed upon with your teacher and peers. Be sure to record quantitative and qualitative data each day. The observations should be recorded on a class chart and in a data table in the computer.

Interpreting Ozone Observations

To read the strips, the color on the ozone test strip should be compared to the Eco Badge® Colorimetric Chart (as shown)

To interpret the meaning of the ozone level, share the data in the ozone conversion table below. The U.S. EPA has established 120 parts per billion of ozone as the optimal level allowable by law. That is, if a reading exceeds 120 ppb (even for one day), then that community is not in compliance. Naturally, some cities have a more serious problem than others. For example, these cities were above the smog level standards an average of the following number of days per year: Los Angeles (155); New York (20); Houston (20); Atlanta (5); Fresno, CA (21); and Bakersfield, CA (29).

Air Quality




1st Stage Alert

2nd Stage Alert

PPB on Eco™Filter

10 - 50

50 - 150

100 -250

250 -350


Part per billion


60 - 120

120 - 190

190 - ;340


Ozone Index reported to public.

(ozone level/120 X100)


50 -100

100 - 150

150 - 280


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