Wildfire smoke across the region may create unhealthy conditions Wednesday, particularly for those with heart and lung conditions.

The Colorado Department of Public Health and Environment issued an Air Quality Health Advisory for Fremont, Teller, Huerfano, Pueblo, El Paso, Elbert and eastern Custer counties. The advisory is in effect until Thursday.

Colorado Gov. Jared Polis urged residents to monitor air quality conditions.

“We’re urging Coloradans, especially those with respiratory conditions, children, and older adults, to limit strenuous or extensive outdoor activity and stay informed as conditions change,” Polis said in a news release.

Wildfire smoke contains fine particles that can irritate the lungs and heart, and it is not always visible to the naked eye, state officials said in a news release.

Those at greater risk of exposure to smoke include children, older adults, pregnant women and women who have recently given birth and those with heart or lung conditions or those exercising outdoors.

Stay indoors if smoke is thick, state officials said.

Residents should also relocate if smoke is present indoors and creating symptoms.

If visibility drops to less than 5 miles, smoke has reached levels that are unhealthy.

Coloradans can protect themselves by taking these actions: 

• Check air quality conditions at Colorado.gov/airquality, Fire.AirNow.gov or through the AirNow mobile app. 
• Sign up to receive CDPHE Air Quality Alerts via email. 
• Review CDPHE air quality advisories and the Colorado Smoke Blog for smoke information. 
• Limit time outdoors when smoke is present.
• Avoid strenuous outdoor activity, including running, biking or mowing the lawn.
• Take steps to maintain a cleaner indoor air space:
  • Keep windows and doors closed when smoke is present. 
  • Use air conditioning on the recirculate setting, if available.
  • Use a HEPA air cleaner in the room where you spend the most time, if available. 
  • Consider spending time at a public space with cleaner indoor air, if you don’t have air conditioning or a HEPA air cleaner at home.
• Consider wearing a well-fitting N95 or KN95 mask if you must be outside.