Friday has been designated a Clean Air Action Day for these counties: Muskegon, Ottawa, Kent, Allegan, Van Buren, Berrien and Cass.
An Action Day is also in effect for NW Indiana (including S. Bend, Elkhart and Gary) and the Detroit area., along with the areas around Indianapolis, Louisville, Washington D.C., Baltimore, Philadelphia and Atlantic City.
Clean Air Action Days started as Ozone Action Days with a one hour standard of 124 parts per billion. The standard was lowered to 75 parts per billion and in 2016 to 70 parts per billion. Days (like tomorrow) that would not have been Ozone Action Days under the old guidelines now qualify under the new guidelines. You can monitor air quality here.