Smoke from wildfires in the western United States and Canada has blanketed much of the country in a thick haze, creating unhealthy air quality as far away as North Carolina.

As of Monday, air quality in the mountains and Piedmont regions of North Carolina remained in the “moderate” range, meaning unusually sensitive people should consider limiting their time in the outdoors.

Experts say smoke from the wildfires could affect parts of North Carolina to a varying degree for several more weeks, depending on the weather.

Here, Jennifer Richmond-Bryant, an associate professor of the practice at North Carolina State University’s College of Natural Resources, explains more about how wildfire smoke affects air quality and human health:

How are wildfires from the West causing hazy skies across the country?

Wildfires generate large quantities of heat, and we know that heat rises. Such intense heat will actually climb into the upper troposphere. The Bootleg Fire in Oregon, covering hundreds of thousands of acres, is generating such large quantities of heat that it is changing local airflow patterns.

At the same time, the Bootleg Fire is producing massive amounts of smoke. The rising heat of the wildfire plume takes with it the fine suspended particles and gases from the smoke. In the jet stream, the pollutants can travel thousands of miles. Fine particles can remain suspended over thousands of miles because they are so small that they do not quickly settle out.

As a result, smoke from the Bootleg Fire has been observed across the country. In recent years, we have seen similar occurrences with other large-scale western fires.

Read the full article about wildfire smoke by Laura Oleniacz at Futurity.