Introduction: First, What is an Aerosol?
An aerosol is a system of tiny particles suspended in a gas. These microscopic particles, solid or liquid, are formed in the atmosphere through two primary mechanisms that result in particles of vastly different sizes.
| Formation Mechanism | Description & Typical Particle Size |
| Nucleation | Formed when vapor molecules from processes like combustion or photochemistry condense together. This mechanism produces very small particles, typically smaller than 0.1 µm in diameter. |
| Comminution | Formed by the mechanical breakup of larger solid or liquid matter, such as through wind erosion or sea spray. This produces larger particles, generally above 1 µm and often exceeding 10 µm in diameter. |
Because aerosols are a complex mixture of particles formed in different ways, simply defining the “size” of a single particle is more challenging than it first appears.