When wildfires burn, they don’t only damage land, homes, and businesses. Wildfire emissions, which can be transported over long distances, can be toxic and contribute to the formation of secondary pollutants such as ozone and fine particles in the atmosphere. Those emissions affect human health and the environment, so scientists want to know what’s in wildfire smoke. According to new research from CIRES and NOAA, what matters most is not what kind of fuel is burning, but the temperature at which it burns.