Fig. 1
24-h average PM2.5 in Salt Lake Valley, UT during Winter 2012-2013. Dashed lines indicate the level of 24-h average PM2.5 designated as “Red Alert” and “Yellow Action” days by the Utah Division of Air Quality. “Red Alert” days are defined by a 24 h average PM2.5 level ≥ 35.5 μg / m3, which is the value which exceeds the National Ambient Air Quality Standards (NAAQS). “Yellow Action” days are defined by a 24 average PM2.5 level ≥ 25.5 μg / m3. Poor air quality testing days included those with 24 h average PM2.5 level ≥ 35.5 μg / m3, or 24 average PM2.5 level ≥ 25.5 μg / m3 with peak PM2.5 ≥ 35.5 μg / m3