Decoding the Air Quality Index and PM Numbers

Estimated read time: 2-3 minutes

This archived news story is available only for your personal, non-commercial use. Information in the story may be outdated or superseded by additional information. Reading or replaying the story in its archived form does not constitute a republication of the story.

Dina Freedman Reporting This year we've seen a lot of red air days and we've been telling you all about it in our forecasts and in the news. We've gotten a lot of inquiries though from YOU, the people at home that want to know what all the numbers about PM 2.5 and Ozone this and that, and what that all means.

Green, yellow and red. We've been hearing a lot about air quality and the colors that correlate to our health and safety. Some new rules have made it more confusing.

Rick Sprott, Director, Utah Division of Air Quality: "In December the EPA made the standard for particulate matter twice as stringent based on health information."

Ok, let's make it simple. The standards for pollution are now higher, so we have more unhealthy air days. PM 2.5 means 'particulate matter', the 2.5 is a measurement in a micron, it's just small that's all.

Ken Symons, Environmental Scientist: "Car exhaust, diesel fumes, diesel exhaust, a little bit of rail road, airplanes, they emit exhaust too."

Donna Spangler, Utah Division of Air Quality: "When the air pollution is high, we don't need to add more vehicles to the road that adds more to the pollution. And 55% of this type of pollution does come from vehicles and only about 15% from wood burning stoves."

This clean filter is what goes in at the beginning of the sampling part of the day, now at the end of the day it looks like this black one. This is the pm 2.5 that's in our air, that's what we've been talking about throughout this story and this black stuff is what you're breathing in.

There are PM numbers and Air Quality Index numbers, but it's the PM 2.5 that you better pay attention to.

Rick Sprott: "For the PM 2.5 standards, the number is now 35, the number last year was 65. That's the number people need to watch."

Once the PM 2.5 levels hit 35, that's the time to be careful outdoors and drive less.

The Department of Air Quality also tells us their new website with easier to read data is going to debut in the next couple of weeks.