Entering the cold and dry winter, people spend more time indoors, which can easily cause indoor air pollution. Indoor air pollution refers to the indoor environment pollution caused by the excess of harmful substances in indoor air. If you breathe the polluted indoor air for a long time, it will endanger your health. There are five main ways to cause indoor air pollution: one is the human body exhaled carbon dioxide and smoke caused by smoking; two is the decoration materials and daily necessities volatile harmful gases; three is with microorganisms, viruses, bacteria, dirty air; four is the cooking fumes in the kitchen; five is the centralized air conditioning system is not clean circulating air. In addition, indoor air pollution is easy to cause harm to the human body. The cold winter climate, people’s indoor activities increased time, indoor carbon dioxide, carbon monoxide, respirable particulates, volatile organic compounds and some pathogenic microorganisms and other harmful substances may bring adverse effects. For example, people who work in a closed indoor air conditioning environment for a long time often feel boredom, fatigue, drowsiness, muscle pain, reduced work efficiency and health status, and a higher chance of catching a cold, which are collectively called “air conditioning syndrome”. Winter is the season of respiratory infectious diseases. People should pay more attention to the hazards caused by indoor air pollution, frail elderly and children and other people with low resistance, try not to go to or less crowded, indoor public places with poor air circulation. Pay attention to ventilation when living at home, especially when using sunny weather to increase the amount of ventilation. People who work for a long time in office buildings, shopping malls and other places where people gather should try to make use of breaks between jobs and do outdoor activities appropriately. Public places using centralized air conditioning should follow the relevant requirements of Beijing’s centralized air conditioning ventilation system management, do a good job of winter management and maintenance of the engine room, units, filters, ventilation ducts, and pay attention to indoor ventilation.