The Advantages of the Four Day Flush

This time of year, it takes about four days to go from clean air to levels that are unhealthy for sensitive groups (i.e., PM2.5 concentrations greater than 35.5 ug/m3 when stagnant conditions build in.

You can see this fairly well in the graph below from the Utah Division of Air Quality sensor at Hawthorne Elementary.  We had clean air (PM2.5 levels less than 10 ug/m2) early yesterday morning, but have risen to about 20 ug/m3 as of about noon today.

Source: Utah Division of Air Quality

Tomorrow we will begin to flirt with 30 ug/m3 and, if the ridge hangs around, we'll be into unhealthy air by Thursday.

However, we have the good fortune of having a weather system moving through Wednesday night, which will give us the much needed "four day flush" to clean things out before things get really bad.