AirCompare - How to Interpret the Results
The height of each bar equals the total number of unhealthy days for each year over the last several years. Three categories of unhealthy days from the Air Quality Index are possible in this graph: orange days (unhealthy for sensitive groups), red days (unhealthy for everyone), and purple days (very unhealthy). If a bar is made up of more than one color, you can see the number of orange days, red days, and/or purple days that add up to the total number of unhealthy days for each year.
This chart uses the height of the bars to show how the total number of unhealthy days has changed in recent years based on the health concern you select. It uses up to three colors in each bar to show how the number of orange, red, and/or purple days has changed over the years.