1. Studying Ozone and Air Quality
Deborah Carlisle
Steve Schneider

2. Measuring Ground-level Ozone
O3 levels above 120 ppb are considered unhealthy. They can be generated by some electrical equipment or from photochemical reactions with smog:
VOC’s + NOX + sunlight  O3
Motor vehicles are the single largest contributor to ground-level ozone.
In this project we are adapting the relatively easy-to-make Schoenbein papers for classroom use, and using ADI to analyze the color changes quantitatively.
Color chart allows for a general

3. Ozone Levels

4. Schoenbein Papers
Ozone was discovered by C.F. Schoenbein in He developed an ozone-sensitive test paper that was widely used historically, and more recently in classrooms.
The standard protocol for using the papers calls for an 8-hour exposure to the air out of direct sunlight. Various studies have shown a dependence on humidity, and there are a variety of recommendations for moistening the strips prior to exposure.
Control low O high O3
exposure exposure
They are relatively easy to make – takes some practice to get an even application of the chemical across the entire filter paper.

5. Historically
Despite the method's early limitations, starting in the mid-1800s, more than 300 stations recorded ozone exposures in countries such as Austria, Australia, Belgium, England, France, Germany, Russia, and the United States.

6. Schoenbein Papers
Cntrl
Cntrl 50 ppb – jpg 735

7. How do Ozone Test Strips Work?
Ozone is a strong oxidizer. It rapidly reacts with the iodide ion, I- in the KI salt applied to the filter paper:
KI + H2O + O3  I2 + O2 + K+
I2 + I- + starch  I3- + starch (turns blue)
Color chart allows for a general – Strips are inside cardboard with cntrl on the left and 140ppb on right
Cntrl
70ppb
100ppb

8. Facilitating Classroom Use:
1. We find that strips can be exposed dry, stored, and then dipped into water just before photographing. The exposed strips react with the water to produce a more uniform and consistent color that appears less dependent on humidity.
2. With digital monitoring devices, we are developing a digital color scale that can be used to test ozone levels after exposures of only two hours.
3. We are also testing and developing digital color calibration for commercial ozone-testing papers, although their cost per test may be prohibitive for many schools.
Color chart allows for a general

9. Outdoor exposure
Distribute teacher notes, and have them turn to pg 4 in handout “Use of Test Strips”

10. Outdoor exposure

11.
Interesting data based on scattered data – based on site
BUT local sources are very relevant and use strip to verify certain areas such as bus stops,

12. Comparing Test Strips

13. Coloration Why and How?? KI + H2O + O3  I2 + O2 + K+
I2 + I- + starch  I3- + starch (turns blue)
Last step : I3- (linear)+ starch (helix)
Combination of I3- and helix causes light reflection to be in the blue/violet range of visible spectrum

15. How do Ozone Test Strips Work?
Ozone is a strong oxidizer. It rapidly reacts with the iodide ion, I- in the KI salt applied to the filter paper:
KI + H2O + O3  I2 + O2 + K+
I2 + I- + starch  I3- + starch (turns blue)
Color chart allows for a general – Strips are inside cardboard with cntrl on the left and 140ppb on right
Cntrl
70ppb
100ppb

16. Calibration of Test Strips
Green wavelength here – rough idea
If G value is below approx. 18 then ppb is greater than 140+

18. Control vs Exposed

19. Comparing to color scale

20. Accurate comparison