1. The basic principle of the internal and external circulation function
The internal and external circulation function means that the device can switch between two modes: internal air circulation and external air introduction circulation. The alternating use of these two modes can effectively improve the air quality and ensure that the indoor air is always fresh and healthy.

Internal air circulation mode: In this mode, the device extracts indoor air through the internal fan and purifies it through the filter, and then releases the clean air back to the room. This can effectively remove harmful substances such as dust, PM2.5, viruses and bacteria in the indoor air.

External air introduction circulation mode: In this mode, the device introduces fresh outdoor air into the room through the external ventilation system, and removes pollutants in the external air through multiple filtration systems to keep the indoor air flowing and fresh.

This flexible switching between internal and external circulation can automatically adjust the wind speed and purification intensity according to the changes in indoor air quality, providing the suitable air quality solution.

2. The role of internal and external circulation mode in improving air quality
The internal and external circulation function of the Wall mounted 500 CADR air fresh ventilation device can achieve continuous improvement of air quality through scientific design, which is specifically manifested in the following aspects:

Removal of harmful substances: In the internal air circulation mode, the device filters out large particles such as dust, pollen, pet dander, etc. in the indoor air through HEPA filters and other high-efficiency filtration systems, and removes PM2.5 particles, carbon dioxide (CO2) and other harmful substances in the air. In addition, the built-in LED ultraviolet lamps in the device can eliminate bacteria and viruses in the air, further improving the cleanliness of the air. This mode is particularly suitable for situations where there are many pollutants in the air, such as smoking, kitchen fumes or pet hair.

Introduction of fresh air: In the external air introduction circulation mode, the device can introduce fresh air from the outside into the room, and remove pollutants such as dust, bacteria and harmful gases in the outdoor air through the built-in filtration system. Especially when the air quality is good, the introduction of external air circulation helps to increase the indoor oxygen concentration, reduce the accumulation of indoor carbon dioxide, and provide a more comfortable and healthy environment for indoor personnel.

3. Internal and external circulation mode and real-time monitoring of air quality
The Wall mounted 500 CADR air fresh ventilation device can automatically sense changes in indoor air quality through real-time air quality monitoring function, and adjust the internal and external circulation mode according to the changes.

When the air quality is relatively good, the device can automatically turn on the external air introduction circulation mode to introduce fresh outdoor air, increase the oxygen content, and prevent the indoor air from becoming stuffy or the carbon dioxide concentration from being too high.

4. Energy saving and efficient air circulation
Through the reasonable switching of internal and external circulation modes, the Wall mounted 500 CADR air fresh ventilation device can not only purify the air efficiently, but also has a good energy-saving effect. Compared with traditional air purifiers, the device can automatically adjust the working mode according to the actual air quality to avoid unnecessary energy consumption.

5. Air circulation and healthy and comfortable living environment
Good air circulation not only helps to remove harmful substances in the air, but also effectively regulates indoor temperature and humidity, further improving the comfort of the living environment. The temperature and humidity display function of the Wall mounted 500 CADR air fresh ventilation device can monitor the indoor temperature and humidity changes in real time, and adjust the wind speed and circulation mode according to the actual situation to ensure that the indoor temperature and humidity are maintained within the suitable range.