In recent years, "smog" weather has appeared frequently, which has seriously affected people's lives. PM2.5 is the main cause of "smog" weather, which is rich in a lot.

(1)PM2.5 is the main cause of "smog", which is rich in toxic and harmful substances, stays in the atmosphere for a long time and has a long transportation distance. Air enters the lungs and passes through the nasal cavity, pharynx, larynx, trachea and bronchus. However, PM2.5 particles are small and are not easily blocked by organs such as the nose. It can directly enter the bronchus and alveoli, affecting the gas exchange in the lungs and causing asthma. It can be seen that PM2.5 mainly harms the human respiratory system.

(2) "Smog" weather is very harmful to human health, and the main cause of "smog" is PM2.5. Therefore, the main measure to avoid the harm of this weather to human health is to reduce the inhalation of PM2.5, which can be achieved by wearing special masks (masks with activated carbon adsorption layers) and minimizing the exposure.

(3) Hazy weather is mainly caused by excessive PM2.5 in the air, which refers to particles with a diameter less than or equal to 2.5 microns in the air. These particles come from the burning of a large number of fossil fuels, so it is necessary to reduce PM2.5 to slow down the haze weather. Therefore, central heating in residential areas, emissions from abandoned factories, and restrictions on even and odd numbers of cars can all reduce smog weather.

So the answer is: (1) Breathe; (2) Wear a special mask (mask with activated carbon adsorption layer) to minimize going out; (3) Central heating in residential areas, emissions from abandoned factories, and restrictions on even and odd car numbers can all reduce smog weather.