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Because you asked: Why is that one monitor green?

A screenshot of the OregonAir app taken on Aug. 1, 2018.

When air quality in the Rogue Valley is unhealthy, we tend to hear the following question a lot: Why is that one monitor green? In a sea of air quality monitors that read orange (unhealthy for sensitive groups) or red (unhealthy) or purple (very unhealthy), a green (good) monitor on the Air Quality Index map tends to stick out. One caller asked the other day: Should we all move to Talent? 

We can't provide real estate advice, but we can say there is a simple reason the monitors are different colors. They're measuring different pollutants.

Some of the sites in the Oregon Department of Environmental Quality's air monitoring network, like Talent that green dot on the screen above, only have ozone monitors. Those monitors will typically appear green in the morning as ozone is an afternoon pollutant. Ozone pollution builds up over the course of a hot sunny day and reaches its peak in the late afternoon and early evening. Ozone forms with sunlight, heat, nitrogen oxide, volatile organic compounds, and low winds. Particulate matter is a primary pollutant in wildfire smoke that can be present anytime under any conditions 

When you're looking at DEQ's Air Quality Index online or on the OregonAir app, make sure you're narrowing your search by pollutant type. The screenshot above is of the OregonAir app. If you're using that, simply hit the pollutants button on the bottom right and select PM2.5 if you're interested in tracking impacts from wildfire sites. PM 2.5 refers to fine particulate matter.  

On the online Air Quality Index, select the PM2.5 button on the left side of your screen. To see all monitors, hit all.

We're not saying to ignore those ozone monitors. Especially on hot days it's good to keep an eye on those and to know what steps you can take to reduce smog and protect your health.

If you have a question you'd like to see addressed in a future blog post, leave us a comment.