The Term Brown air is used for
The term Brown air is used for Photochemical smog. This smog is a type of air pollution. This is a mixture of smoke and fog. It was first described in the 1950s. When nitrogen oxides and volatile organic compounds (VOCs) react to sunlight, creating a brown mist above cities. It tends to occur more often in summer, because that is when we have the utmost sunlight.
Photochemical smog is composed of primary and secondary pollutants.
Primary Pollutants: The two major primary pollutants, nitrogen oxides and VOCs, combine to change in sunlight in a series of chemical reactions, outlined below, to create what are known as secondary pollutants
Secondary Pollutants: The secondary pollutant that causes the most concern in the ozone that forms at ground level. While ozone is produced naturally in the upper atmosphere, it is a dangerous substance when found at ground level. Many other hazardous substances are also formed, such as peroxyacetyl nitrate.