Flag definitions used by the EPA's Air Quality System (US Environmental Protection Agency ) , as provided by the EPA. An additional column with the corresponding NARSTO flags was added by the ASRC.
aqs_flagsAn object of class data.frame with 163 rows and 7 columns.
US Environmental Protection Agency (????). “Air Quality System Data Mart.” type: dataset, https://aqs.epa.gov/aqsweb/documents/data_mart_welcome.html.