Canada has already had its share of wildfires this season, and the smoke from these wildfires is slowly drifting south over the United States' Midwest. The drifting smoke can be seen in this Terra satellite image over Lake Michigan, as well as parts of Minnesota, Wisconsin, Indiana and Ohio. The smoke released by any type of fire (forest, brush, crop, structure, tires, waste or wood burning) is a mixture of particles and chemicals produced by incomplete burning of carbon-containing materials. All smoke contains carbon monoxide, carbon dioxide and particulate matter (PM or soot). Smoke can contain many different chemicals, including aldehydes, acid gases, sulfur dioxide, nitrogen oxides, polycyclic aromatic hydrocarbons (PAHs), benzene, toluene, styrene, metals and dioxins.