This article will help you understand the numbers on the Kaiterra Web App, how we calculate the Overall Index, and the different breakpoints for pollutants and their Color Scale.
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Overall Index and Color Scale
Kaiterra created the Overall Index to provide an at-a-glance, holistic view of your air, while simultaneously letting you know which air pollutant to tackle first. Utilizing the same methodology and breakpoints as the EPA's AQI standard, an index is calculated for each individual pollutant, and the highest index is displayed as the Overall Index.
The breakpoints used for calculating Overall Index values, as well as their corresponding color and category, are displayed in the table below. 
The table of breakpoints is also a valuable tool for interpreting your air quality readings. When looking at the Overall Index, your air quality is good if it is below 50, with some variation between pollutant concentrations. If your Overall Index value is high, then taking a look at the primary pollutant and the individual pollutant concentrations will inform you which pollutant you should focus on.
Converting Pollutant Concentration to Overall Index
The index conversion algorithm is a piecewise linear function of the pollutant concentration. At the boundary between AQI categories, such as the boundary between Good and Moderate AQI values, there is a discontinuous jump of one AQI unit.
To convert from concentration to AQI, this equation is used:
To illustrate how this conversion works, suppose a monitor records a fine particle (PM2.5) concentration of 12.0 µg/m³. Applying the equation above, this PM2.5 concentration converts:
When multiple air pollutants are measured, the highest resulting index value is displayed, and the Sensedge will indicate the primary pollutants on the "My Air" view.
If you have any questions regarding how to view, interpret, or convert your air quality readings, please reach out by submitting or a support ticket or emailing us at info@kaiterra.com.