Haze over Denver north to Fort Collins has prompted the Colorado Department of Public Health and Environment (CDPHE) to issue an Action Day.
The poor air quality is expected to effect the Denver-Boulder metropolitan area until at least 4 p.m. Friday.
According to the CDPHE, stagnant weather conditions have allowed fine particles to concentrate enough that the air is unhealthy for sensitive groups. This is most prevalent in the northern parts of the Denver metro area, and Boulder, Longmont, Fort Collins and Greeley and the surrounding areas. Residents in these areas may notice poor visibility outside.
Click here for a detailed summary of the air quality in these locations.
As of 11 a.m., the highest air quality index (AQI) value for a particulate less than 2.5 micrometers was 105. AQI runs between 0 and 500, with higher numbers indicating a greater level of air pollution and, therefore, health concern. Learn more about the AQI level breakdown here.
People with heart disease or lung disease, plus older adults and children, should reduce prolonged or heavy exertions outside Friday, the CDPHE said.