Air Quality Index: What is it and what do those numbers mean?

Bay Area

We’ve been talking a lot this week about the horrible air quality in the Bay Area that’s due to the lingering smoke from the Camp Fire burning in Butte County. 

The Bay will see some relief next week as we get closer to Thanksgiving. 

Until then, many parts of the Bay are unfortunately stuck with these poor air quality conditions for the rest of the week and into the weekend. 

Of course, some areas are getting hit worse than others. 

Take the Tri-Valley for example. Livermore, Pleasanton, and Dublin are the worst hit right now, according to KRON4 meteorologist John Shrable. 

Now how is it assessed that some areas are worse than others? 

That’s when the Air Quality Index (AQI) comes in handy. 

It’s an index that tells you how clean or polluted the air, and what associated health effects might be a concern for you as a result. 

According to the Environmental Protection Agency, the AQI calculates the AQI for five major air pollutants regulated by the Clean Air Act: 

  • ground-level ozone 
  • particle pollution (also known as particulate matter) 
  • carbon monoxide 
  • sulfur dioxide 
  • nitrogen dioxide 

The AQI is much like a yardstick that measures from 0 to 500. 

The higher the AQI, the greater the level of air pollution and the greater health concern.For example, the AQI in Santa Clara Thursday morning is measured at 115, “unhealthy for sensitive groups.” Bad, but not too bad. 

Livermore is clocking in at 158, “unhealthy” (for everyone). 

>> Click here to see the map via Bay Area Air Quality Management District. 

It’s worse as you go further north, where the Camp Fire is burning. 

Chico is measuring at more than 300 — that’s considered “hazardous.”

Each section is also color coded. 

If you’ve heard us say “San Francisco is in a Code Red” as we’ve been doing this past week, that basically means “unhealthy” air conditions. 

You can see the color codes in the graph above. 

The most important question — when will the Bay Area see some relief and go back into “green” aka good air quality? 

Try next week as we get closer to Thanksgiving. We’re even expecting some rain! 

Stay with KRON4 for the latest updates. 



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