In fact the air quality was poor enough that the 24-hour average Hydrogen Sulfide (H2S) level at the Liberty monitor exceeded the state limit Sunday—finishing the day at 0.008 ppm according to initial data from the Allegheny County Health Department (ACHD). The limit is 0.005 ppm.
That means that the H2S standard has been exceeded 10 times so far in 2020.
Unless conditions improve this afternoon, there will likely be another exceedance of the H2S standard today.
For those keeping track: The 24-hour average concentration of H2S at the Liberty monitor was also exceeded on March 2.