DENVER (KDVR) -- The seven-county Denver-Boulder metro area was placed under an Action Day for Visibility by the state health department due to low visibility Wednesday afternoon into Thursday.

According to the Colorado Department of Public Health and Environment, the metro region's air quality was rated "moderate" and visibility on Thursday was projected to be "poor." The Action Day was in effect from 4 p.m. on Wednesday through 4 p.m. on Thursday.

The seven-county region impacted includes Denver, Boulder, Broomfield, Douglas, Jefferson, and areas west of Kiowa Creek in Adams and Arapahoe counties.

Action days are called by the state health department when fine particulate matter, carbon monoxide, ozone or other air pollutants are creating unhealthy air quality conditions. The days typically indicate the air quality will be either "unhealthy" or "unhealthy for sensitive groups" categories under the Air Quality Index.

Wednesday's Action Day for Visibility noted that unusually sensitive people should consider reducing prolonged or heavy exertion.

Because of this, the agency requested that individuals limit driving any gas or diesel-powered vehicles through at least 4 p.m. on Thursday, and to limit indoor burning. Some wood-burning devices are exempt from burning restrictions, which can be explored here.

CDPHE cited "limited atmospheric mixing and ventilation" that is expected to limit air quality and create moderate to poor visibility on Thursday.