How many foggy days are there in Beijing?

There are about half foggy days in Beijing a year, and most of them are not obvious. Severe visible haze weather is about forty or fifty days.

Haze is very harmful to human body. Smog weather should minimize travel time and protect your nose and mouth when traveling. It is recommended to install a fresh air system at home. My home decoration is five degrees and five constants, and the effect is very good. The indoor PM2.5 concentration in foggy days is only about 10.