The above image is the USA EPA AQI. It’s this index you find quoted on apps like Weather on the iPhone and mentioned on local radio stations or news reports etc. It was this index going into the red area in 2018 and 2020 that prompted the creation of this website.
EPA AQI
The EPA AQI is made up of 5 different pollutants, namely, Ground level Ozone, Particulate Matter, Carbon Monoxide, Sulfur dioxide and Nitrogen dioxide. The actual index is calculated from all 5 of these pollutants. You can find the maths at USA EPA AQI
Particulate Matter PM2.5
In the Bay Area the AQI is dominated by PM2.5, especially when there are wildfires. This is why the part of the AQI that I’m interested in PM2.5 i.e. particulate matter of 2.5 microns and below in size. These size particulates have an outsized impact on our health.
EPA PM2.5 Guide
Filtering Air
It’s actually much simpler than what a lot of companies would have you believe to have clean air in your home and it doesn’t require expensive equipment. There is a DIY Air Filter for about $70, where a replacement filter can be as cheap as $10 and it will filter the air in your home effectively.