A gaseous dispersion system consisting of solid or liquid particles suspended in a gaseous medium. The density of these solid or liquid particles can vary greatly from the density of the gas medium. The size of the particles is generally from 0.001~100μm. The shape of the particles can be almost spherical, such as liquid fog beads, can also be flaky, needle-like and other irregular shape. In engineering technology, especially in labor protection and environmental protection engineering, in order to distinguish between clean air, the use of dust-containing gases or polluting gases is commonly used to address aerosols. From the point of view of hydrodynamics, aerosol is essentially a multiphase fluid with a gaseous phase, solid and liquid phase.
Aerosols are divided into smoke, mist, and dust, which are naturally produced or artificially formed. Aerosols that are less than 10μm solid particles obtained by physical or chemical condensation are called smoke. Aerosols formed in the vapor condensation or liquid dispersion process are called fog. When solids are dispersed, aerosols that are larger than 10μm solid particles are called dust. Aerosols, in most cases, are coarse dispersions, so they are rapidly settling in the surface aerosol in a spontaneous process that can cause their own destruction: the adhesion (condensation) of particles, the confluence (coalescence) of vapour droplets, deposition (sedimentation), evaporation, isothermal sublimation. Under the influence of the above process, the initial concentration of the particles (the number of particles in a cubic centimeter) drops sharply. The effects of filtration, electric field or ultrasonic field, the change of aerosol flow (cyclone), the introduction of the crystallization center which can increase the aerosol particles and the introduction of condensation nuclei are all the processes of destroying aerosol. Aerosols are militarily significant in the use of chemical agents, usually to make agents into aerosol states. To form large areas of air, ground and objects to be poisoned. A radioactive aerosol is generated during a nuclear explosion, which can drift to a very long distance from the air flow and cause air pollution, and the ground (along the tracks of the Radioactive smoke movement) can be contaminated by the settlement of the larger particles. Aerosols can be used to form a masking screen. In volume explosive ordnance, the use of combustion substances (mixed fuel) to generate aerosol clouds, the cloud explosion has a strong destructive force. Aerosols produced in the living environment (submarines, spaceships, etc.) are harmful. In order to create normal conditions for people's lives in such confined spaces, the idea is to remove aerosols.