Activity 3: Using an Ozone Isopleth Graph

This activity should be done with the Ozone Isopleth Graph, shown below.

Explanation:

Suppose that the design ratio in the interface is 10:1.
Draw a line from the origin to the tip of your number of NO_x.
How many ppms of VOCs to NO_x does it take to create a ratio of 10 to 1?
The Daily Design Value should be 0.160 ppms of O₃.
The Target Design value of O3 is 0.12 ppms of O₃.

Calculations:

Once the line is drawn, find the intersection of the Volatile Organic Compounds and the number of Nitrogen Oxides through the point on the line which goes with the Daily Design Ratio
This intersection of VOC's and NO_x is the result of a base case.
To calculate what has to be done in the future to get the better ozone, each value is taken and multiplied by any control strategy percent (10%, 20%, 30%, etc.).
Let's suppose our control strategy is 20%, we take our NO_x future case and multiply by (1-.80) to obtain our future value. The result for this example should be 0.10.
Look back into the graph and you will find that the reduction of VOC at 0.10 is approximately 0.40.
How should VOC be reduced then?
Now, take the starting VOC and ending VOC and calculate what reduction has to be done for it in the future case. The equation should be:

Starting VOC x (1 - % decrease) = Ending VOC
1.20 x (1 - % decrease) = 0.40
(1 - % decrease) = 0.40
% decrease = 0.33

This means that in the future case we have to reduce VOC by 67%.
Let's double check this percentage with the model used to calculate these percentages. Go to Basic Interface and run the model does not require any input except the Daily design value to be 0.16 ppm's of O3 and the experimental design ratio should be 10:1.
Once the model is run, look in the hc table again and use the interpolating calculator to compare the model's number with the calculated one and the result might vary just a bit.
You might get 45% instead of 67% . The answer is close!

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