ការព្យាករណ៍គុណភាពខ្យល់
ទិន្នន័យគុណភាពខ្យល់ផ្តល់ដោយ៖ the Colorado Department of Environmental Protection (colorado.gov)
Note that the measurements for CO (carbon monoxide), NO2 (nitrogen dioxide) and SO2 (sulfur dioxide) are taken from the station: USA:Colorado/Welch