Abstract: By comparing the change trend of indoor CO₂ concentration in different scenarios of power on and power off, the positive influence of the fresh fan on reducing CO₂ concentration in the room was proved. Indoor different initial concentration of indoor CO₂ concentration had a greater influence on the change trend, the initial concentration higher than that of dynamic balance, during using it the display of CO₂ concentration shows the reduce of the trend, while the initial concentration is lower than the dynamic balance, CO₂ concentration shows rising trend, which may cause complaints by market consumers. Based on the theoretical calculation and experimental data to provide data support for market complaints, reduce use erroneous zone. Different fresh air volumes have a great influence on the decline trend of indoor CO₂ concentration and the dynamic equilibrium point, so users need to choose the use scene with appropriate fresh air volume according to the use demand. It is of great significance to promote the application of fresh fans and improve people's cognition.

Key words: Fresh air system, CO₂ concentration, Dynamic equilibrium point