Air quality science looks at the degree to which the ambient air contains pollution. There are several factors that can affect air quality, both natural—such as from volcanic eruptions or dust—as well as human-induced. Significant outdoor sources of anthropogenic air pollution include carbon dioxide (CO₂) from vehicles and aircraft, as well as methane (CH₄) and ammonia (NH₃) from raising livestock. Indoor sources include formaldehyde (H₂CO) from household products and carbon monoxide (CO) from gas stoves. Air quality monitoring networks include satellites, airborne sampling, and ground methods. Explore the Air Quality Resource Center