Things that move like cars, construction equipment, lawn mowers, all terrain vehicles, and boats. These types of sources are called mobile or non-point sources . Things that grow like trees and grass and flowers. These are called biogenic sources . NOx is usually a by- product of high temperature combustion.
Common sources are cars and power plants.
VOCs include organic chemicals that vaporize easily, like gasoline. In addition to NOx, VOCs, and ground-level ozone Texas air contains particulate matter. These are tiny bits of dust, ash, and other materials. When you see a dust cloud you are seeing particulate matter. Much of the matter is so small you can't see it, but you can see its effect.