Fog and haze are aerosols. Aerosols are liquid or solid particles suspended in the air, they can participate in various chemical cycles and are important constituents of the atmosphere. The usual fog, smoke and haze as well as light fog, fine dust and smog are atmospheric aerosols caused by natural or man-made causes. These suspended tiny particles are generally between 0.001-100 μm in diameter, with liquid particles called fog and particles smaller than 1 μm called dust. Aerosols can be divided into floating dust and dustfall according to their sizes. Dustfall particles with diameters >10μm are likely to settle down quickly under their own gravity, while floating dust may float in the atmosphere for a long time and have a greater impact on humans. As the particle diameter <10μm drifting dust is easy to be inhaled and absorbed by the human body, it is also called inhalable particles, i.e. IPM. If the particularly small aerosol particles, whose radius is <0.1μm, are lighter in weight, mainly distributed at high altitude, can drift away with the wind, and are unlikely to be absorbed by the human body. However, in an unventilated environment, aerosols containing viruses can stay in the air for a long time. To prevent aerosols, you should always wear a mask, such as a medical N95 mask, when you go out. At the same time, we should pay attention to ventilation in the home environment and keep the air circulating to avoid aerosols staying in the home for a long time. Content source: Dr. You Lai