In 1958, Europe took the lead in proposing the concept of modern indoor fresh air. At that time, for the sake of energy conservation, the air tightness of buildings was greatly improved, resulting in insufficient indoor ventilation rate, resulting in frequent indoor air pollution incidents. Some people have symptoms such as headache, dry cough, dry and itchy skin, dizziness and nausea, difficulty concentrating, and sensitivity to odors. This condition, known as "pathogenic Jianzonghe syndrome", occurs in many countries, and all developed countries have learned painful lessons in this regard. This makes people begin to study and explore the impact of indoor air quality on human health, pollutants and their sources, and feasible solutions. As a result, in the economy, science and technology developed and pay attention to the quality of life in Europe, there has been a residential microcirculation air replacement system, referred to as VMC is commonly known as the central fresh air system. It is a continuous and can control the ventilation path of ventilation, through the good performance of the fan and air flow control system, so that the replacement of fresh air is completely controlled, this technology has little effect on indoor temperature. Under the premise of not opening the window, the indoor dirty air is continuously discharged in time 24 hours a day, and the outdoor fresh air is introduced and the air volume is effectively controlled. VMC systems are installed in more than 90 per cent of newly built homes. In 2000, the VMC has become a statute throughout the EU countries.