Particulates – The finely divided solid or liquid particles that are suspended in the air is known as particulates. Some of the examples of particulates present in the air or atmosphere such as Fumes, Spray, Fly-Ash, Dust, Mist, and Smoke. Particulates are a kind of air pollutants that can be solid or liquids such as smoke, dust and fumes are solid particulates while spray and mist are liquid particulates.

There are some other examples of particulates in the atmosphere such as bacteria, spores, pollen-grains, viruses, hair, sodium chloride, insecticides, lead dust, asbestos, and fur. The particulates are categorized as per their size, physical state or source such as smokes, fumes and aerosols are solid or liquid particulates whose particles have a diameter of less than ‘’one micrometer’’. The large solid particles whose diameter is more than ‘’one micrometer’’ are called dust while liquid particles of diameter more than one diameter are known as mists.

Now discuss some of the particulates in details are as given below –

• Mist – These are suspensions of liquid particles in the air which arise from atomization of liquids, condensation of vapors, and chemical reaction.
• Dust – The small solid particles which are temporarily suspended in the air are called dust. The dust particles do not disperse in air and sometimes settle down on the surface of the earth due to the force of gravity.
• Aerosol – The extremely fine particles of solids or liquids that are suspended in the air are called aerosols. Fog and Smoke are the two commo examples of aerosols. The particles of aerosols are so small that they behave almost like gases. The aerosols remain suspended in air indefinitely and move with air currents and other disturbances in the air.
• Fog – The minute water particles which are suspended in the air near the surface of the earth are known as fog. The fog particles are produced by the condensation of water vapor that are present in the air and it occurs especially the winter season.
• Fumes – They are made up of minute solid particles which is formed by the condensation of vapors during distillation, sublimation, calcination, or other metallurgical and chemical processes.
• Droplets – The small particles of water or any other liquid that can fall down when the air is still but remain suspended in the air in turbulent conditions are known as droplets.
• Fly-Ash – The small particles are formed by the combustion of fossil fuels such as coal are carried into the air by the gases produced during combustion and form fly-ash. The fly-ash also contains partially burnt particles of the fuel. There are some examples of fly-ash such as coal ash and ash coming out from a boiler. The chimneys of coal-based thermal power emit a lot of fly-ash that pollutes the air.