The atmosphere is composed of gases, water vapour, and dust particles. These three components form the fundamental building blocks of the atmospheric envelope surrounding the Earth.

The proportion of gases changes in the higher layers of the atmosphere. At the height of 120 km, oxygen becomes almost negligible in quantity. Similarly, carbon dioxide and water vapour are found only up to 90 km from the surface of the Earth.

Dust particles are small solid particles that the atmosphere has a sufficient capacity to keep. These originate from different sources including sea salts, fine soil, smoke-soot, ash, pollen, dust, and disintegrated particles of meteors. Dust particles are generally concentrated in the lower layers of the atmosphere, though convectional air currents may transport them to great heights.

The concentration of dust particles varies across regions. A higher concentration is found in subtropical and temperate regions due to dry winds, in comparison to equatorial and polar regions.

Dust and salt particles play an important role as hygroscopic nuclei around which water vapour condenses to produce clouds. The troposphere contains both dust particles and water vapour.