Particulate Matter (PM)

Particulate Matter or PM is made up of soot, dust, and vehicle emissions and is usually a winter time problem. It is measured in two sizes, 2.5 and 10.

  • PM10 can be filtered by nose hair and lung cilia and coughed out.
  • PM2.5 is small enough to get past these natural defense systems. When breathed in, PM2.5 can get deep into the lungs where it becomes trapped and sticks around, aggravating current health problems like asthma.

PM is most noticed during Utah's Inversions.

Inversions form when the right weather conditions--cold temperatures, no breezes—cause the cold air to become trapped.

Symptom Tracking Sheet - A sheet to assist in tracking PM2.5 levels and your symptoms to plan physical activity.


  • During an inversion normal conditions (cool air above and warm air below) are switched or inverted and a layer of warm air traps a layer of cold air in the valley.
  • The warm air acts like a lid trapping pollutants near the valley floor. The longer the inversion lasts, the more pollutants become trapped.

An inversion will stay until wind or a storm front comes through. The "typical" period is from a few days to a week. The longer the inversion lasts, the more pollution there is in the air.