July is generally the  peak month in the April through October “ozone season” in Nevada County.  And sure enough, yesterday we had a warning of dangerous ground-level ozone measurements, no doubt aggravated by the Robbers Fire near Colfax, which is still ongoing.

I was especially frustrated by that alert, because I am now well into our summer regimen of opening most of our house windows early in morning to let in cool air, shutting them during the peak hot hours of the day, then opening them again in the evening for a period of “fresh” air before bedtime (we usually leave our bedroom windows open all night in summer months). But last night, not only did I not open the windows in the evening, I also left them closed all night, because I had mistakenly thought that ozone levels peak at about 4 AM.

Well, I wish I had looked at the STAINC website before going to bed! “STAINC” stands for “Save The Air in Nevada County, and the website is a very useful repository of both up-to-the-hour ozone monitoring data as well as tutorials on the science of ozone pollution.

In fact, ozone concentration peaked yesterday at about 10 PM, then fell continuously all night to well into the “good” zone by 4 AM.

Especially useful is the following video tutorial by Dr. Jeff Kane: